Technique for performing multi-link communication in wireless communication system

ABSTRACT

According to various embodiments, a multi-link device operating in a plurality of links can transmit, via a first link, a request frame for changing the first link from among the plurality of links to a second link not included in the plurality of links. The multi-link device can receive a response frame via the first link on the basis of the request frame. The multi-link device can change the first link to the second link on the basis of the response frame.

FIELD OF THE DISCLOSURE

The present specification relates to a technique for performingmulti-link communication in a wireless local area network (WLAN) systemand, more particularly, to a method for transmitting information on alink in multi-link communication and an apparatus for supporting thesame.

RELATED ART

Wireless network technologies may include various types of wirelesslocal area networks (WLANs). The WLAN employs widely used networkingprotocols and can be used to interconnect nearby devices together. Thevarious technical features described herein may be applied to anycommunication standard, such as Wi-Fi or, more generally, any one of theIEEE 802.11 family of wireless protocols. A wireless local area network(WLAN) has been enhanced in various ways. For example, the IEEE 802.11axstandard has proposed an enhanced communication environment by usingorthogonal frequency division multiple access (OFDMA) and downlinkmulti-user multiple input multiple output (DL MU MIMO) schemes.

The present specification proposes a technical feature that can beutilized in a new communication standard. For example, the newcommunication standard may be an extreme high throughput (EHT) standardwhich is currently being discussed. The EHT standard may use anincreased bandwidth, an enhanced PHY layer protocol data unit (PPDU)structure, an enhanced sequence, a hybrid automatic repeat request(HARQ) scheme, or the like, which is newly proposed. The EHT standardmay be called the IEEE 802.11be standard.

SUMMARY

In the EHT standard, a wide bandwidth (e.g., 160/320 MHz), 16 streams,and/or a multi-link (or multi-band) operation may be used to supporthigh throughput and high data rate.

In the EHT standard, a device supporting a multi-link (i.e., amulti-link device) may operate in a plurality of links. To change aconnected link, the multi-link device needs to receive information on adifferent link other than a link included in the plurality of links.Accordingly, a technical feature for the multi-link device to receivethe information on the different link and to change the connected linkbased on the information may be required.

According to various embodiments, a multi-link device (MLD) operating ina plurality of links may perform: an operation of transmitting a requestframe for changing a first link among the plurality of links to a secondlink not included in the plurality of links through the first link; anoperation of receiving a response frame through the first link, based onthe request frame, the response frame including first information on thesecond link; and an operation of changing the first link to the secondlink based on the response frame.

A STA included in a multi-link device may also transmit information onanother STA in the multi-link device through one link. Accordingly, itis possible to reduce overhead of a frame exchange. In addition, it ispossible to increase link use efficiency of the STA and to reduce powerconsumption.

Further, a first STA included in the multi-link device may requestpartial information by each link. For example, the first STA of themulti-link device may request partial information on a second link, andmay receive the partial information.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a transmitting apparatus and/or receivingapparatus of the present specification.

FIG. 2 is a conceptual view illustrating the structure of a wirelesslocal area network (WLAN).

FIG. 3 illustrates a general link setup process.

FIG. 4 illustrates an example of a PPDU used in an IEEE standard.

FIG. 5 illustrates an operation based on UL-MU.

FIG. 6 illustrates an example of a trigger frame.

FIG. 7 illustrates an example of a common information field of a triggerframe.

FIG. 8 illustrates an example of a subfield included in a per userinformation field.

FIG. 9 illustrates an example of a channel used/supported/defined withina 2.4 GHz band.

FIG. 10 illustrates an example of a channel used/supported/definedwithin a 5 GHz band.

FIG. 11 illustrates an example of a channel used/supported/definedwithin a 6 GHz band.

FIG. 12 shows an example of a HE-PPDU.

FIG. 13 illustrates an example of a PPDU used in the presentspecification.

FIG. 14 illustrates an example of a modified transmission device and/orreceiving device of the present specification.

FIG. 15 illustrates an example of channel bonding.

FIG. 16 illustrates an example of the structure of a non-AP MLD.

FIG. 17 illustrates an example in which an AP MLD and a non-AP MLD areconnected through a link setup process.

FIG. 18 illustrates an example in which a link is changed orreconnected.

FIG. 19 illustrates a specific example in which a link is changed orreconnected.

FIG. 20 illustrates the operations of an AP MLD and a non-AP MLD for alink change or reconnection.

FIG. 21 illustrates the operations of an AP MLD and a non-AP MLD for alink change or reconnection.

FIG. 22 illustrates the operations of an AP MLD and a non-AP MLD for alink change or reconnection.

FIG. 23 illustrates an example of a link re-setup process.

FIG. 24 illustrates another example of a link re-setup process.

FIG. 25 illustrates another example of a link re-setup process.

FIG. 26 illustrates another example of a link re-setup process.

FIG. 27 illustrates another example of a link re-setup process.

FIG. 28 illustrates another example of a link re-setup process.

FIG. 29 illustrates an example of a link switching negotiation processand a link re-setup process.

FIG. 30 illustrates an example in which information for link re-setup istransmitted through a separate frame.

FIG. 31 illustrates an example in which information for link re-setup istransmitted through a confirmation frame.

FIG. 32 illustrates an example in which information for link re-setup istransmitted through a link switching request frame.

FIG. 33 illustrates an example in which information for link re-setup istransmitted through a link switching response frame.

FIG. 34 illustrates an example in which information for link re-setup istransmitted through a link switching request/response frame.

FIG. 35 illustrates an example in which information for link re-setup istransmitted through a separate frame.

FIG. 36 illustrates an example of a link switching negotiation processand an information transmission process for link re-setup.

FIG. 37 illustrates an example of a power saving operation of a non-APMLD after a link change.

FIG. 38 illustrates an example of a power saving operation of a non-APMLD after a link change.

FIG. 39 illustrates an example of a power saving operation of a non-APMLD after a link change.

FIG. 40 illustrates an example of a link re-setup operation of a STAwhen the STA switches a link from AP MLD 2 to AP MLD 1.

FIG. 41 illustrates an example of a link re-setup process when a link isswitched to a different AP MLD other than a connected AP MLD.

FIG. 42 illustrates another example of a link re-setup process when alink is switched to a different AP MLD other than a connected AP MLD.

FIG. 43 illustrates another example of a link re-setup process when alink is switched to a different link of a connected AP MLD.

FIG. 44 illustrates another example of a link re-setup process when alink is switched to a different link of a connected AP MLD.

FIG. 45 is a flowchart illustrating the operation of a multi-linkdevice.

FIG. 46 is a flowchart illustrating the operation of an AP multi-linkdevice.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the present specification, “A or B” may mean “only A”, “only B” or“both A and B”. In other words, in the present specification, “A or B”may be interpreted as “A and/or B”. For example, in the presentspecification, “A, B, or C” may mean “only A”, “only B”, “only C”, or“any combination of A, B, C”.

A slash (/) or comma used in the present specification may mean“and/or”. For example, “A/B” may mean “A and/or B”. Accordingly, “A/B”may mean “only A”, “only B”, or “both A and B”. For example, “A, B, C”may mean “A, B, or C”.

In the present specification, “at least one of A and B” may mean “onlyA”, “only B”, or “both A and B”. In addition, in the presentspecification, the expression “at least one of A or B” or “at least oneof A and/or B” may be interpreted as “at least one of A and B”.

In addition, in the present specification, “at least one of A, B, and C”may mean “only A”, “only B”, “only C”, or “any combination of A, B, andC”. In addition, “at least one of A, B, or C” or “at least one of A, B,and/or C” may mean “at least one of A, B, and C”.

In addition, a parenthesis used in the present specification may mean“for example”. Specifically, when indicated as “control information(EHT-signal)”, it may denote that “EHT-signal” is proposed as an exampleof the “control information”. In other words, the “control information”of the present specification is not limited to “EHT-signal”, and“EHT-signal” may be proposed as an example of the “control information”.In addition, when indicated as “control information (i.e., EHT-signal)”,it may also mean that “EHT-signal” is proposed as an example of the“control information”.

Technical features described individually in one figure in the presentspecification may be individually implemented, or may be simultaneouslyimplemented.

The following example of the present specification may be applied tovarious wireless communication systems. For example, the followingexample of the present specification may be applied to a wireless localarea network (WLAN) system. For example, the present specification maybe applied to the IEEE 802.11a/g/n/ac standard or the IEEE 802.11axstandard. In addition, the present specification may also be applied tothe newly proposed EHT standard or IEEE 802.11be standard. In addition,the example of the present specification may also be applied to a newWLAN standard enhanced from the EHT standard or the IEEE 802.11bestandard. In addition, the example of the present specification may beapplied to a mobile communication system. For example, it may be appliedto a mobile communication system based on long term evolution (LTE)depending on a 3^(rd) generation partnership project (3GPP) standard andbased on evolution of the LTE. In addition, the example of the presentspecification may be applied to a communication system of a 5G NRstandard based on the 3GPP standard.

Hereinafter, in order to describe a technical feature of the presentspecification, a technical feature applicable to the presentspecification will be described.

FIG. 1 shows an example of a transmitting apparatus and/or receivingapparatus of the present specification.

In the example of FIG. 1 , various technical features described belowmay be performed. FIG. 1 relates to at least one station (STA). Forexample, STAs 110 and 120 of the present specification may also becalled in various terms such as a mobile terminal, a wireless device, awireless transmit/receive unit (WTRU), a user equipment (UE), a mobilestation (MS), a mobile subscriber unit, or simply a user. The STAs 110and 120 of the present specification may also be called in various termssuch as a network, a base station, a node-B, an access point (AP), arepeater, a router, a relay, or the like. The STAs 110 and 120 of thepresent specification may also be referred to as various names such as areceiving apparatus, a transmitting apparatus, a receiving STA, atransmitting STA, a receiving device, a transmitting device, or thelike.

For example, the STAs 110 and 120 may serve as an AP or a non-AP. Thatis, the STAs 110 and 120 of the present specification may serve as theAP and/or the non-AP.

The STAs 110 and 120 of the present specification may support variouscommunication standards together in addition to the IEEE 802.11standard. For example, a communication standard (e.g., LTE, LTE-A, 5G NRstandard) or the like based on the 3GPP standard may be supported. Inaddition, the STA of the present specification may be implemented asvarious devices such as a mobile phone, a vehicle, a personal computer,or the like. In addition, the STA of the present specification maysupport communication for various communication services such as voicecalls, video calls, data communication, and self-driving(autonomous-driving), or the like.

The STAs 110 and 120 of the present specification may include a mediumaccess control (MAC) conforming to the IEEE 802.11 standard and aphysical layer interface for a radio medium.

The STAs 110 and 120 will be described below with reference to asub-figure (a) of FIG. 1 .

The first STA 110 may include a processor 111, a memory 112, and atransceiver 113. The illustrated process, memory, and transceiver may beimplemented individually as separate chips, or at least twoblocks/functions may be implemented through a single chip.

The transceiver 113 of the first STA performs a signaltransmission/reception operation. Specifically, an IEEE 802.11 packet(e.g., IEEE 802.11a/b/g/n/ac/ax/be, etc.) may be transmitted/received.

For example, the first STA 110 may perform an operation intended by anAP. For example, the processor 111 of the AP may receive a signalthrough the transceiver 113, process a reception (RX) signal, generate atransmission (TX) signal, and provide control for signal transmission.The memory 112 of the AP may store a signal (e.g., RX signal) receivedthrough the transceiver 113, and may store a signal (e.g., TX signal) tobe transmitted through the transceiver.

For example, the second STA 120 may perform an operation intended by anon-AP STA. For example, a transceiver 123 of a non-AP performs a signaltransmission/reception operation. Specifically, an IEEE 802.11 packet(e.g., IEEE 802.11a/b/g/n/ac/ax/be packet, etc.) may betransmitted/received.

For example, a processor 121 of the non-AP STA may receive a signalthrough the transceiver 123, process an RX signal, generate a TX signal,and provide control for signal transmission. A memory 122 of the non-APSTA may store a signal (e.g., RX signal) received through thetransceiver 123, and may store a signal (e.g., TX signal) to betransmitted through the transceiver.

For example, an operation of a device indicated as an AP in thespecification described below may be performed in the first STA 110 orthe second STA 120. For example, if the first STA 110 is the AP, theoperation of the device indicated as the AP may be controlled by theprocessor 111 of the first STA 110, and a related signal may betransmitted or received through the transceiver 113 controlled by theprocessor 111 of the first STA 110. In addition, control informationrelated to the operation of the AP or a TX/RX signal of the AP may bestored in the memory 112 of the first STA 110. In addition, if thesecond STA 120 is the AP, the operation of the device indicated as theAP may be controlled by the processor 121 of the second STA 120, and arelated signal may be transmitted or received through the transceiver123 controlled by the processor 121 of the second STA 120. In addition,control information related to the operation of the AP or a TX/RX signalof the AP may be stored in the memory 122 of the second STA 120.

For example, in the specification described below, an operation of adevice indicated as a non-AP (or user-STA) may be performed in the firstSTA 110 or the second STA 120. For example, if the second STA 120 is thenon-AP, the operation of the device indicated as the non-AP may becontrolled by the processor 121 of the second STA 120, and a relatedsignal may be transmitted or received through the transceiver 123controlled by the processor 121 of the second STA 120. In addition,control information related to the operation of the non-AP or a TX/RXsignal of the non-AP may be stored in the memory 122 of the second STA120. For example, if the first STA 110 is the non-AP, the operation ofthe device indicated as the non-AP may be controlled by the processor111 of the first STA 110, and a related signal may be transmitted orreceived through the transceiver 113 controlled by the processor 111 ofthe first STA 110. In addition, control information related to theoperation of the non-AP or a TX/RX signal of the non-AP may be stored inthe memory 112 of the first STA 110.

In the specification described below, a device called a(transmitting/receiving) STA, a first STA, a second STA, a STA1, a STA2,an AP, a first AP, a second AP, an AP1, an AP2, a(transmitting/receiving) terminal, a (transmitting/receiving) device, a(transmitting/receiving) apparatus, a network, or the like may imply theSTAs 110 and 120 of FIG. 1 . For example, a device indicated as, withouta specific reference numeral, the (transmitting/receiving) STA, thefirst STA, the second STA, the STA1, the STA2, the AP, the first AP, thesecond AP, the AP1, the AP2, the (transmitting/receiving) terminal, the(transmitting/receiving) device, the (transmitting/receiving) apparatus,the network, or the like may imply the STAs 110 and 120 of FIG. 1 . Forexample, in the following example, an operation in which various STAstransmit/receive a signal (e.g., a PPDU) may be performed in thetransceivers 113 and 123 of FIG. 1 . In addition, in the followingexample, an operation in which various STAs generate a TX/RX signal orperform data processing and computation in advance for the TX/RX signalmay be performed in the processors 111 and 121 of FIG. 1 . For example,an example of an operation for generating the TX/RX signal or performingthe data processing and computation in advance may include: 1) anoperation ofdetermining/obtaining/configuring/computing/decoding/encoding bitinformation of a sub-field (SIG, STF, LTF, Data) included in a PPDU; 2)an operation of determining/configuring/obtaining a time resource orfrequency resource (e.g., a subcarrier resource) or the like used forthe sub-field (SIG, STF, LTF, Data) included the PPDU; 3) an operationof determining/configuring/obtaining a specific sequence (e.g., a pilotsequence, an STF/LTF sequence, an extra sequence applied to SIG) or thelike used for the sub-field (SIG, STF, LTF, Data) field included in thePPDU; 4) a power control operation and/or power saving operation appliedfor the STA; and 5) an operation related todetermining/obtaining/configuring/decoding/encoding or the like of anACK signal. In addition, in the following example, a variety ofinformation used by various STAs fordetermining/obtaining/configuring/computing/decoding/decoding a TX/RXsignal (e.g., information related to a field/subfield/controlfield/parameter/power or the like) may be stored in the memories 112 and122 of FIG. 1 .

The aforementioned device/STA of the sub-figure (a) of FIG. 1 may bemodified as shown in the sub-figure (b) of FIG. 1 . Hereinafter, theSTAs 110 and 120 of the present specification will be described based onthe sub-figure (b) of FIG. 1 .

For example, the transceivers 113 and 123 illustrated in the sub-figure(b) of FIG. 1 may perform the same function as the aforementionedtransceiver illustrated in the sub-figure (a) of FIG. 1 . For example,processing chips 114 and 124 illustrated in the sub-figure (b) of FIG. 1may include the processors 111 and 121 and the memories 112 and 122. Theprocessors 111 and 121 and memories 112 and 122 illustrated in thesub-figure (b) of FIG. 1 may perform the same function as theaforementioned processors 111 and 121 and memories 112 and 122illustrated in the sub-figure (a) of FIG. 1 .

A mobile terminal, a wireless device, a wireless transmit/receive unit(WTRU), a user equipment (UE), a mobile station (MS), a mobilesubscriber unit, a user, a user STA, a network, a base station, aNode-B, an access point (AP), a repeater, a router, a relay, a receivingunit, a transmitting unit, a receiving STA, a transmitting STA, areceiving device, a transmitting device, a receiving apparatus, and/or atransmitting apparatus, which are described below, may imply the STAs110 and 120 illustrated in the sub-figure (a)/(b) of FIG. 1 , or mayimply the processing chips 114 and 124 illustrated in the sub-figure (b)of FIG. 1 . That is, a technical feature of the present specificationmay be performed in the STAs 110 and 120 illustrated in the sub-figure(a)/(b) of FIG. 1 , or may be performed only in the processing chips 114and 124 illustrated in the sub-figure (b) of FIG. 1 . For example, atechnical feature in which the transmitting STA transmits a controlsignal may be understood as a technical feature in which a controlsignal generated in the processors 111 and 121 illustrated in thesub-figure (a)/(b) of FIG. 1 is transmitted through the transceivers 113and 123 illustrated in the sub-figure (a)/(b) of FIG. 1 . Alternatively,the technical feature in which the transmitting STA transmits thecontrol signal may be understood as a technical feature in which thecontrol signal to be transferred to the transceivers 113 and 123 isgenerated in the processing chips 114 and 124 illustrated in thesub-figure (b) of FIG. 1 .

For example, a technical feature in which the receiving STA receives thecontrol signal may be understood as a technical feature in which thecontrol signal is received by means of the transceivers 113 and 123illustrated in the sub-figure (a) of FIG. 1 . Alternatively, thetechnical feature in which the receiving STA receives the control signalmay be understood as the technical feature in which the control signalreceived in the transceivers 113 and 123 illustrated in the sub-figure(a) of FIG. 1 is obtained by the processors 111 and 121 illustrated inthe sub-figure (a) of FIG. 1 . Alternatively, the technical feature inwhich the receiving STA receives the control signal may be understood asthe technical feature in which the control signal received in thetransceivers 113 and 123 illustrated in the sub-figure (b) of FIG. 1 isobtained by the processing chips 114 and 124 illustrated in thesub-figure (b) of FIG. 1 .

Referring to the sub-figure (b) of FIG. 1 , software codes 115 and 125may be included in the memories 112 and 122. The software codes 115 and126 may include instructions for controlling an operation of theprocessors 111 and 121. The software codes 115 and 125 may be includedas various programming languages.

The processors 111 and 121 or processing chips 114 and 124 of FIG. 1 mayinclude an application-specific integrated circuit (ASIC), otherchipsets, a logic circuit and/or a data processing device. The processormay be an application processor (AP). For example, the processors 111and 121 or processing chips 114 and 124 of FIG. 1 may include at leastone of a digital signal processor (DSP), a central processing unit(CPU), a graphics processing unit (GPU), and a modulator and demodulator(modem). For example, the processors 111 and 121 or processing chips 114and 124 of FIG. 1 may be SNAPDRAGON™ series of processors made byQualcomm®, EXYNOS™ series of processors made by Samsung®, A series ofprocessors made by Apple®, HELIO™ series of processors made byMediaTek®, ATOM™ series of processors made by Intel® or processorsenhanced from these processors.

In the present specification, an uplink may imply a link forcommunication from a non-AP STA to an SP STA, and an uplinkPPDU/packet/signal or the like may be transmitted through the uplink. Inaddition, in the present specification, a downlink may imply a link forcommunication from the AP STA to the non-AP STA, and a downlinkPPDU/packet/signal or the like may be transmitted through the downlink.

FIG. 2 is a conceptual view illustrating the structure of a wirelesslocal area network (WLAN).

An upper part of FIG. 2 illustrates the structure of an infrastructurebasic service set (BSS) of institute of electrical and electronicengineers (i.e.EE) 802.11.

Referring the upper part of FIG. 2 , the wireless LAN system may includeone or more infrastructure BSSs 200 and 205 (hereinafter, referred to asBSS). The BSSs 200 and 205 as a set of an AP and a STA such as an accesspoint (AP) 225 and a station (STA1) 200-1 which are successfullysynchronized to communicate with each other are not concepts indicatinga specific region. The BSS 205 may include one or more STAs 205-1 and205-2 which may be joined to one AP 230.

The BSS may include at least one STA, APs providing a distributionservice, and a distribution system (DS) 210 connecting multiple APs.

The distribution system 210 may implement an extended service set (ESS)240 extended by connecting the multiple BSSs 200 and 205. The ESS 240may be used as a term indicating one network configured by connectingone or more APs 225 or 230 through the distribution system 210. The APincluded in one ESS 240 may have the same service set identification(SSID).

A portal 220 may serve as a bridge which connects the wireless LANnetwork (i.e. EE 802.11) and another network (e.g., 802.X).

In the BSS illustrated in the upper part of FIG. 2 , a network betweenthe APs 225 and 230 and a network between the APs 225 and 230 and theSTAs 200-1, 205-1, and 205-2 may be implemented. However, the network isconfigured even between the STAs without the APs 225 and 230 to performcommunication. A network in which the communication is performed byconfiguring the network even between the STAs without the APs 225 and230 is defined as an Ad-Hoc network or an independent basic service set(IBSS).

A lower part of FIG. 2 illustrates a conceptual view illustrating theIBSS.

Referring to the lower part of FIG. 2 , the IBSS is a BSS that operatesin an Ad-Hoc mode. Since the IBSS does not include the access point(AP), a centralized management entity that performs a managementfunction at the center does not exist. That is, in the IBSS, STAs 250-1,250-2, 250-3, 255-4, and 255-5 are managed by a distributed manner. Inthe IBSS, all STAs 250-1, 250-2, 250-3, 255-4, and 255-5 may beconstituted by movable STAs and are not permitted to access the DS toconstitute a self-contained network.

FIG. 3 illustrates a general link setup process.

In S310, a STA may perform a network discovery operation. The networkdiscovery operation may include a scanning operation of the STA. Thatis, to access a network, the STA needs to discover a participatingnetwork. The STA needs to identify a compatible network beforeparticipating in a wireless network, and a process of identifying anetwork present in a particular area is referred to as scanning.Scanning methods include active scanning and passive scanning.

FIG. 3 illustrates a network discovery operation including an activescanning process. In active scanning, a STA performing scanningtransmits a probe request frame and waits for a response to the proberequest frame in order to identify which AP is present around whilemoving to channels. A responder transmits a probe response frame as aresponse to the probe request frame to the STA having transmitted theprobe request frame. Here, the responder may be a STA that transmits thelast beacon frame in a BSS of a channel being scanned. In the BSS, sincean AP transmits a beacon frame, the AP is the responder. In an IBSS,since STAs in the IBSS transmit a beacon frame in turns, the responderis not fixed. For example, when the STA transmits a probe request framevia channel 1 and receives a probe response frame via channel 1, the STAmay store BSS-related information included in the received proberesponse frame, may move to the next channel (e.g., channel 2), and mayperform scanning (e.g., transmits a probe request and receives a proberesponse via channel 2) by the same method.

Although not shown in FIG. 3 , scanning may be performed by a passivescanning method. In passive scanning, a STA performing scanning may waitfor a beacon frame while moving to channels. A beacon frame is one ofmanagement frames in IEEE 802.11 and is periodically transmitted toindicate the presence of a wireless network and to enable the STAperforming scanning to find the wireless network and to participate inthe wireless network. In a BSS, an AP serves to periodically transmit abeacon frame. In an IBSS, STAs in the IBSS transmit a beacon frame inturns. Upon receiving the beacon frame, the STA performing scanningstores information related to a BSS included in the beacon frame andrecords beacon frame information in each channel while moving to anotherchannel. The STA having received the beacon frame may store BSS-relatedinformation included in the received beacon frame, may move to the nextchannel, and may perform scanning in the next channel by the samemethod.

After discovering the network, the STA may perform an authenticationprocess in S320. The authentication process may be referred to as afirst authentication process to be clearly distinguished from thefollowing security setup operation in S340. The authentication processin S320 may include a process in which the STA transmits anauthentication request frame to the AP and the AP transmits anauthentication response frame to the STA in response. The authenticationframes used for an authentication request/response are managementframes.

The authentication frames may include information related to anauthentication algorithm number, an authentication transaction sequencenumber, a status code, a challenge text, a robust security network(RSN), and a finite cyclic group.

The STA may transmit the authentication request frame to the AP. The APmay determine whether to allow the authentication of the STA based onthe information included in the received authentication request frame.The AP may provide the authentication processing result to the STA viathe authentication response frame.

When the STA is successfully authenticated, the STA may perform anassociation process in S330. The association process includes a processin which the STA transmits an association request frame to the AP andthe AP transmits an association response frame to the STA in response.The association request frame may include, for example, informationrelated to various capabilities, a beacon listen interval, a service setidentifier (SSID), a supported rate, a supported channel, RSN, amobility domain, a supported operating class, a traffic indication map(TIM) broadcast request, and an interworking service capability. Theassociation response frame may include, for example, information relatedto various capabilities, a status code, an association ID (AID), asupported rate, an enhanced distributed channel access (EDCA) parameterset, a received channel power indicator (RCPI), a receivedsignal-to-noise indicator (RSNI), a mobility domain, a timeout interval(association comeback time), an overlapping BSS scanning parameter, aTIM broadcast response, and a QoS map.

In S340, the STA may perform a security setup process. The securitysetup process in S340 may include a process of setting up a private keythrough four-way handshaking, for example, through an extensibleauthentication protocol over LAN (EAPOL) frame.

FIG. 4 illustrates an example of a PPDU used in an IEEE standard.

As illustrated, various types of PHY protocol data units (PPDUs) areused in IEEE a/g/n/ac standards. Specifically, an LTF and a STF includea training signal, a SIG-A and a SIG-B include control information for areceiving STA, and a data field includes user data corresponding to aPSDU (MAC PDU/aggregated MAC PDU).

FIG. 4 also includes an example of an HE PPDU according to IEEE802.11ax. The HE PPDU according to FIG. 4 is an illustrative PPDU formultiple users. An HE-SIG-B may be included only in a PPDU for multipleusers, and an HE-SIG-B may be omitted in a PPDU for a single user.

As illustrated in FIG. 4 , the HE-PPDU for multiple users (MUs) mayinclude a legacy-short training field (L-STF), a legacy-long trainingfield (L-LTF), a legacy-signal (L-SIG), a high efficiency-signal A(HE-SIG A), a high efficiency-signal-B (HE-SIG B), a highefficiency-short training field (HE-STF), a high efficiency-longtraining field (HE-LTF), a data field (alternatively, an MAC payload),and a packet extension (PE) field. The respective fields may betransmitted for illustrated time periods (i.e., 4 or 8 μs).

Hereinafter, a resource unit (RU) used for a PPDU is described. An RUmay include a plurality of subcarriers (or tones). An RU may be used totransmit a signal to a plurality of STAs according to OFDMA. Further, anRU may also be defined to transmit a signal to one STA. An RU may beused for an STF, an LTF, a data field, or the like.

FIG. 5 illustrates an operation based on UL-MU. As illustrated, atransmitting STA (e.g., an AP) may perform channel access throughcontending (e.g., a backoff operation), and may transmit a trigger frame530. That is, the transmitting STA may transmit a PPDU including thetrigger frame 530. Upon receiving the PPDU including the trigger frame,a trigger-based (TB) PPDU is transmitted after a delay corresponding toSIFS.

TB PPDUs 541 and 542 may be transmitted at the same time period, and maybe transmitted from a plurality of STAs (e.g., user STAs) having AIDsindicated in the trigger frame 530. An ACK frame 550 for the TB PPDU maybe implemented in various forms.

A specific feature of the trigger frame is described with reference toFIG. 6 to FIG. 8 . Even if UL-MU communication is used, an orthogonalfrequency division multiple access (OFDMA) scheme or a MU MIMO schememay be used, and the OFDMA and MU-MIMO schemes may be simultaneouslyused.

FIG. 6 illustrates an example of a trigger frame. The trigger frame ofFIG. 6 allocates a resource for uplink multiple-user (MU) transmission,and may be transmitted, for example, from an AP. The trigger frame maybe configured of a MAC frame, and may be included in a PPDU.

Each field shown in FIG. 6 may be partially omitted, and another fieldmay be added. In addition, a length of each field may be changed to bedifferent from that shown in the figure.

A frame control field 610 of FIG. 6 may include information related to aMAC protocol version and extra additional control information. Aduration field 620 may include time information for NAV configuration orinformation related to an identifier (e.g., AID) of a STA.

In addition, an RA field 630 may include address information of areceiving STA of a corresponding trigger frame, and may be optionallyomitted. A TA field 640 may include address information of a STA (e.g.,an AP) which transmits the corresponding trigger frame. A commoninformation field 650 includes common control information applied to thereceiving STA which receives the corresponding trigger frame. Forexample, a field indicating a length of an L-SIG field of an uplink PPDUtransmitted in response to the corresponding trigger frame orinformation for controlling content of a SIG-A field (i.e., HE-SIG-Afield) of the uplink PPDU transmitted in response to the correspondingtrigger frame may be included. In addition, as common controlinformation, information related to a length of a CP of the uplink PPDUtransmitted in response to the corresponding trigger frame orinformation related to a length of an LTF field may be included.

In addition, per user information fields 660 #1 to 660 #N correspondingto the number of receiving STAs which receive the trigger frame of FIG.6 are preferably included. The per user information field may also becalled an “allocation field”.

In addition, the trigger frame of FIG. 6 may include a padding field 670and a frame check sequence field 680.

Each of the per user information fields 660 #1 to 660 #N shown in FIG. 6may include a plurality of subfields.

FIG. 7 illustrates an example of a common information field of a triggerframe. A subfield of FIG. 7 may be partially omitted, and an extrasubfield may be added. In addition, a length of each subfieldillustrated may be changed.

A length field 710 illustrated has the same value as a length field ofan L-SIG field of an uplink PPDU transmitted in response to acorresponding trigger frame, and a length field of the L-SIG field ofthe uplink PPDU indicates a length of the uplink PPDU. As a result, thelength field 710 of the trigger frame may be used to indicate the lengthof the corresponding uplink PPDU.

In addition, a cascade identifier field 720 indicates whether a cascadeoperation is performed. The cascade operation implies that downlink MUtransmission and uplink MU transmission are performed together in thesame TXOP. That is, it implies that downlink MU transmission isperformed and thereafter uplink MU transmission is performed after apre-set time (e.g., SIFS). During the cascade operation, only onetransmitting device (e.g., AP) may perform downlink communication, and aplurality of transmitting devices (e.g., non-APs) may perform uplinkcommunication.

A CS request field 730 indicates whether a wireless medium state or aNAV or the like is necessarily considered in a situation where areceiving device which has received a corresponding trigger frametransmits a corresponding uplink PPDU.

An HE-SIG-A information field 740 may include information forcontrolling content of a SIG-A field (i.e., HE-SIG-A field) of theuplink PPDU in response to the corresponding trigger frame.

A CP and LTF type field 750 may include information related to a CPlength and LTF length of the uplink PPDU transmitted in response to thecorresponding trigger frame. A trigger type field 760 may indicate apurpose of using the corresponding trigger frame, for example, typicaltriggering, triggering for beamforming, a request for block ACK/NACK, orthe like.

It may be assumed that the trigger type field 760 of the trigger framein the present specification indicates a trigger frame of a basic typefor typical triggering. For example, the trigger frame of the basic typemay be referred to as a basic trigger frame.

FIG. 8 illustrates an example of a subfield included in a per userinformation field. A user information field 800 of FIG. 8 may beunderstood as any one of the per user information fields 1160 #1 to 1160#N mentioned above with reference to FIG. 11 . A subfield included inthe user information field 80 of FIG. 8 may be partially omitted, and anextra subfield may be added. In addition, a length of each subfieldillustrated may be changed.

A user identifier field 810 of FIG. 8 indicates an identifier of a STA(i.e., receiving STA) corresponding to per user information. An exampleof the identifier may be the entirety or part of an associationidentifier (AID) value of the receiving STA.

In addition, an RU allocation field 820 may be included. That is, whenthe receiving STA identified through the user identifier field 810transmits a TB PPDU in response to the trigger frame, the TB PPDU istransmitted through an RU indicated by the RU allocation field 820.

The subfield of FIG. 8 may include a coding type field 830. The codingtype field 830 may indicate a coding type of the TB PPDU. For example,when BCC coding is applied to the TB PPDU, the coding type field 830 maybe set to ‘1’, and when LDPC coding is applied, the coding type field830 may be set to ‘0’.

In addition, the subfield of FIG. 8 may include an MCS field 840. TheMCS field 840 may indicate an MCS scheme applied to the TB PPDU. Forexample, when BCC coding is applied to the TB PPDU, the coding typefield 830 may be set to ‘1’, and when LDPC coding is applied, the codingtype field 830 may be set to ‘0’.

FIG. 9 illustrates an example of a channel used/supported/defined withina 2.4 GHz band.

The 2.4 GHz band may be called in other terms such as a first band. Inaddition, the 2.4 GHz band may imply a frequency domain in whichchannels of which a center frequency is close to 2.4 GHz (e.g., channelsof which a center frequency is located within 2.4 to 2.5 GHz) areused/supported/defined.

A plurality of 20 MHz channels may be included in the 2.4 GHz band. 20MHz within the 2.4 GHz may have a plurality of channel indices (e.g., anindex 1 to an index 14). For example, a center frequency of a 20 MHzchannel to which a channel index 1 is allocated may be 2.412 GHz, acenter frequency of a 20 MHz channel to which a channel index 2 isallocated may be 2.417 GHz, and a center frequency of a 20 MHz channelto which a channel index N is allocated may be (2.407+0.005*N) GHz. Thechannel index may be called in various terms such as a channel number orthe like. Specific numerical values of the channel index and centerfrequency may be changed.

FIG. 9 exemplifies 4 channels within a 2.4 GHz band. Each of 1st to 4thfrequency domains 910 to 940 shown herein may include one channel. Forexample, the 1st frequency domain 910 may include a channel 1 (a 20 MHzchannel having an index 1). In this case, a center frequency of thechannel 1 may be set to 2412 MHz. The 2nd frequency domain 920 mayinclude a channel 6. In this case, a center frequency of the channel 6may be set to 2437 MHz. The 3rd frequency domain 930 may include achannel 11. In this case, a center frequency of the channel 11 may beset to 2462 MHz. The 4th frequency domain 940 may include a channel 14.In this case, a center frequency of the channel 14 may be set to 2484MHz.

FIG. 10 illustrates an example of a channel used/supported/definedwithin a 5 GHz band.

The 5 GHz band may be called in other terms such as a second band or thelike. The 5 GHz band may imply a frequency domain in which channels ofwhich a center frequency is greater than or equal to 5 GHz and less than6 GHz (or less than 5.9 GHz) are used/supported/defined. Alternatively,the 5 GHz band may include a plurality of channels between 4.5 GHz and5.5 GHz. A specific numerical value shown in FIG. 10 may be changed.

A plurality of channels within the 5 GHz band include an unlicensednational information infrastructure (UNII)-1, a UNII-2, a UNII-3, and anISM. The INII-1 may be called UNII Low. The UNII-2 may include afrequency domain called UNII Mid and UNII-2Extended. The UNII-3 may becalled UNII-Upper.

A plurality of channels may be configured within the 5 GHz band, and abandwidth of each channel may be variously set to, for example, 20 MHz,40 MHz, 80 MHz, 160 MHz, or the like. For example, 5170 MHz to 5330 MHzfrequency domains/ranges within the UNII-1 and UNII-2 may be dividedinto eight 20 MHz channels. The 5170 MHz to 5330 MHz frequencydomains/ranges may be divided into four channels through a 40 MHzfrequency domain. The 5170 MHz to 5330 MHz frequency domains/ranges maybe divided into two channels through an 80 MHz frequency domain.Alternatively, the 5170 MHz to 5330 MHz frequency domains/ranges may bedivided into one channel through a 160 MHz frequency domain.

FIG. 11 illustrates an example of a channel used/supported/definedwithin a 6 GHz band.

The 6 GHz band may be called in other terms such as a third band or thelike. The 6 GHz band may imply a frequency domain in which channels ofwhich a center frequency is greater than or equal to 5.9 GHz areused/supported/defined. A specific numerical value shown in FIG. 11 maybe changed.

For example, the 20 MHz channel of FIG. 11 may be defined starting from5.940 GHz. Specifically, among 20 MHz channels of FIG. 11 , the leftmostchannel may have an index 1 (or a channel index, a channel number,etc.), and 5.945 GHz may be assigned as a center frequency. That is, acenter frequency of a channel of an index N may be determined as(5.940+0.005*N) GHz.

Accordingly, an index (or channel number) of the 2 MHz channel of FIG.11 may be 1, 5, 9, 13, 17, 21, 25, 29, 33, 37, 41, 45, 49, 53, 57, 61,65, 69, 73, 77, 81, 85, 89, 93, 97, 101, 105, 109, 113, 117, 121, 125,129, 133, 137, 141, 145, 149, 153, 157, 161, 165, 169, 173, 177, 181,185, 189, 193, 197, 201, 205, 209, 213, 217, 221, 225, 229, 233. Inaddition, according to the aforementioned (5.940+0.005*N) GHz rule, anindex of the 40 MHz channel of FIG. 11 may be 3, 11, 19, 27, 35, 43, 51,59, 67, 75, 83, 91, 99, 107, 115, 123, 131, 139, 147, 155, 163, 171,179, 187, 195, 203, 211, 219, 227.

Although 20, 40, 80, and 160 MHz channels are illustrated in the exampleof FIG. 11 , a 240 MHz channel or a 320 MHz channel may be additionallyadded.

Hereinafter, a PPDU transmitted/received in a STA of the presentspecification will be described.

FIG. 12 shows an example of a HE-PPDU.

The illustrated L-STF 1200 may include a short training orthogonalfrequency division multiplexing symbol (OFDM). The L-STF 1200 may beused for frame detection, automatic gain control (AGC), diversitydetection, and coarse frequency/time synchronization.

The L-LTF 1210 may include a long training orthogonal frequency divisionmultiplexing symbol (OFDM). The L-LTF 1210 may be used for finefrequency/time synchronization and channel estimation.

The L-SIG 1220 may be used to transmit control information. The L-SIG1220 may include information related to a data transmission rate and adata length. Also, the L-SIG 1220 may be repeatedly transmitted. Thatis, the L-SIG 1220 may be configured in a repeated format (e.g., may bereferred to as R-LSIG).

The HE-SIG-A 1230 may include control information common to thereceiving station(s).

Specifically, the HE-SIG-A 1230 may include information related to: 1) aDL/UL indicator; 2) a BSS color field that is an identifier of the BSS;3) a field indicating the remaining time of the current TXOPduration/period; 4) a Bandwidth field indicating whether 20, 40, 80,160, 80+80 MHz; 5) a field indicating MCS scheme applied to theHE-SIG-B; 6) an indication field indicating whether modulation dualsubcarrier modulation (DCM) is applied to the HE-SIG-B for MCS; 7) afield indicating the number of symbols used for HE-SIG-B; 8) a fieldindicating whether the HE-SIG-B is generated over the full/entire band;9) a field indicating the number of symbols of the HE-LTF; 10) a fieldindicating a length of the HE-LTF and a CP length; 11) a fieldindicating whether additional OFDM symbols exist for LDPC coding; 12) afield indicating control information on Packet Extension (PE); and/or13) a field indicating information related to a CRC field of theHE-SIG-A, and the like. At least one field of the HE-SIG-A may beomitted or changed. In addition, some fields may be added or omitted inother environments where the HE-SIG-A is not a multi-user (MU)environment.

Also, the HE-SIG-A 1230 may be composed of two parts: HE-SIG-A1 andHE-SIG-A2. The HE-SIG-A1 and HE-SIG-A2 included in the HE-SIG-A may bedefined in the following format structure (field) according to acorresponding PPDU. First, the HE-SIG-A field of the HE SU PPDU may bedefined as follows.

TABLE 1 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionHE-SIG-A1 B0 Format 1 Differentiate an HE SU PPDU and HE ER SU PPDU froman HE TB PPDU: Set to 1 for an HE SU PPDU and HE ER SU PPDU B1 Beam 1Set to 1 to indicate that the pre-HE modulated fields of Change the PPDUare spatially mapped differently from the first symbol of the HE-LTF.Equation (28-6), Equation (28-9), Equation (28-12), Equation (28-14),Equation (28-16) and Equation (28-18) apply if the Beam Change field isset to 1. Set to 0 to indicate that the pre-HE modulated fields of thePPDU are spatially mapped the same way as the first symbol of the HE-LTFon each tone. Equation (28- 8), Equation (28-10), Equation (28-13),Equation (28- 15), Equation (28-17) and Equation (28-19) apply if theBeam Change field is set to 0. B2 UL/DL 1 Indicates whether the PPDU issent UL or DL. Set to the value indicated by the TXVECTOR parameterUPLINK_FLAG. B3-B6 MCS 4 For an HE SU PPDU: Set to n for MCSn, where n =0, 1, 2, . . . , 11 Values 12-15 are reserved For HE ER SU PPDU withBandwidth field set to 0 (242-tone RU): Set to n for MCSn, where n = 0,1, 2 Values 3-15 are reserved For HE ER SU PPDU with Bandwidth field setto 1 (upper frequency 106-tone RU): Set to 0 for MCS 0 Values 1-15 arereserved

TABLE 2 Two Parts of Number HE-SIG-A Bit Field of bits Description B7DCM 1 Indicates whether or not DCM is applied to the Data field for theMCS indicated. If the STBC field is 0, then set to 1 to indicate thatDCM is applied to the Data field. Neither DCM nor STBC shall be appliedif both the DCM and STBC are set to 1. Set to 0 to indicate that DCM isnot applied to the Data field. NOTE-DCM is applied only to HE-MCSs 0, 1,3 and 4. DCM is applied only to 1 and 2 spatial streams. DCM is notapplied in combination with STBC B8-B13 BSS Color 6 The BSS Color fieldis an identifier of the BSS. Set to the value of the TXVECTOR parameterBSS_-COLOR. B14 Reserved 1 Reserved and set to 1 B15-B18 Spatial Reuse 4Indicates whether or not spatial reuse is allowed during thetransmission of this PPDU Set to a value from Table 28-21 (Spatial Reusefield encoding for an HE SU PPDU, HE ER SU PPDU, and HE MU PPDU), see27.11.6 (SPATIAL_REUSE). Set to SRP_DISALLOW to prohibit SRP-basedspatial reuse during this PPDU. Set toSRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP- based spatialreuse and non-SRG OBSS PD-based spatial reuse during this PPDU. For theinterpretation of other values see 27.11.6 (SPATIAL_REUSE) and 27.9(Spatial reuse operation). B19-B20 Bandwidth 2 For an HE SU PPDU: Set to0 for 20 MHz Set to 1 for 40 MHz Set to 2 for 80 MHz Set to 3 for 160MHz and 80 + 80 MHz For an HE ER SU PPDU: Set to 0 for 242-tone RU Setto 1 for upper frequency 106-tone RU within the primary 20 MHz Values 2and 3 are reserved

TABLE 3 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionB21-B22 GI + LTF Size 2 Indicates the GI duration and HE-LTF size. Setto 0 to indicate a 1x HE-LTF and 0.8 μs GI Set to 1 to indicate a 2xHE-LTF and 0.8 μs GI Set to 2 to indicate a 2x HE-LTF and 1.6 μs GI Setto 3 to indicate: a 4x HE-LTF and 0.8 μs GI if both the DCM and STBCfields are 1. Neither DCM nor STBC shall be applied if both the DCM andSTBC fields are set to 1. a 4x HE-LTF and 3.2 μs GI, otherwise B23-B25NSTS And 3 If the Doppler field is 0, indicates the number of space-Midamble time streams. Periodicity Set to the number of space-timestreams minus 1 For an HE ER SU PPDU, values 2 to 7 are reserved If theDoppler field is 1, then B23-B24 indicates the number of space timestreams, up to 4, and B25 indicates the midamble periodicity. B23-B24 isset to the number of space time streams minus 1. For an HE ER SU PPDU,values 2 and 3 are reserved B25 is set to 0 if TXVECTOR parameterMIDAMBLE_PERIODICITY is 10 and set to 1 if TXVECTOR parameterMIDAMBLE_PERIODICITY is 20. HE-SIG-A2 B0-B6 TXOP 7 Set to 127 toindicate no duration information (HE SU PPDU) or if TXVECTOR parameterTXOP_DURATION HE-SIG-A3 is set to UNSPECIFIED. (HE ER SU PPDU) Set to avalue less than 127 to indicate duration information for NAV setting andprotection of the TXOP as follows: If TXVECTOR parameter TXOP_DURAT1ONis less than 512, then B0 is set to 0 and B1-B6 is set tofloor(TXOP_DURATION/8). Otherwise, B0 is set to 1 and B1-B6 is set tofloor ((TXOP_DURATION − 512)/128) where B0 indicates the TXOP lengthgranularity. Set to 0 for 8 μs; otherwise set to 1 for 128 μs. B1-B6indicates the scaled value of the TXOP_DURATION B7 Coding 1 Indicateswhether BCC or LDPC is used: Set to 0 to indicate BCC Set to 1 toindicate LDPC

TABLE 4 Two Parts of Number HE-SIG-A Bit Field of bits Description B8LDPC Extra 1 Indicates the presence of the extra OFDM symbol Symbolsegment for LDPC: Segment Set to 1 if an extra OFDM symbol segment forLDPC is present Set to 0 if an extra OFDM symbol segment for LDPC is notpresent Reserved and set to 1 if the Coding field is set to 0 B9 STBC 1If the DCM field is set to 0, then set to 1 if space time block codingis used. Neither DCM nor STBC shall be applied if both the DCM field andSTBC field are set to 1. Set to 0 otherwise. B10 Beam- 1 Set to 1 if abeamforming steering matrix is applied to formed the waveform in an SUtransmission. Set to 0 otherwise. B11-B12 Pre-FEC 2 Indicates thepre-FEC padding factor. Padding Set to 0 to indicate a pre-FEC paddingfactor of 4 Factor Set to 1 to indicate a pre-FEC padding factor of 1Set to 2 to indicate a pre-FEC padding factor of 2 Set to 3 to indicatea pre-FEC padding factor of 3 B13 PE Disambiguity 1 Indicates PEdisambiguity as defined in 28.3.12 (Packet extension). B14 Reserved 1Reserved and set to 1 B15 Doppler 1 Set to 1 if one of the followingapplies: The number of OFDM symbols in the Data field is larger than thesignaled midamble periodicity plus 1 and the midamble is present Thenumber of OFDM symbols in the Data field is less than or equal to thesignaled midamble periodicity plus 1 (sec 28.3.11.16 Midamble), themidamble is not present, but the channel is fast varying. It recommendsthat midamble may be used for the PPDUs of the reverse link. Set to 0otherwise. B16-B19 CRC 4 CRC for bits 0-41 of the HE-SIG-A field (see28.3.10.7.3 (CRC computation)). Bits 0-41 of the HE-SIG-A fieldcorrespond to bits 0-25 of HE-SIG-A1 followed by bits 0-15 ofHE-SIG-A2). B20-B25 Tail 6 Used to terminate the trellis of theconvolutional decoder. Set to 0.

In addition, the HE-SIG-A field of the HE MU PPDU may be defined asfollows.

TABLE 5 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionHE-SIG-A1 B0 UL/DL 1 Indicates whether the PPDU is sent UL or DL. Set tothe value indicated by the TXVECTOR parameter UPLINK_FLAG. NOTE-The TDLSpeer can identify the TDLS frame by To DS and From DS fields in the MACheader of the MPDU. B1-B3 SIGB MCS 3 Indicates the MCS of the HE-SIG-Bfield: Set to 0 for MCS 0 Set to 1 for MCS 1 Set to 2 for MCS 2 Set to 3for MCS 3 Set to 4 for MCS 4 Set to 5 for MCS 5 The values 6 and 7 arereserved B4 SIGB DCM 1 Set to 1 indicates that the HE-SIG-B is modulatedwith DCM for the MCS. Set to 0 indicates that the HE-SIG-B is notmodulated with DCM for the MCS. NOTE-DCM is only applicable to MCS 0,MCS 1, MCS 3, and MCS 4. B5-B10 BSS Color 6 The BSS Color field is anidentifier of the BSS. Set to the value of the TXVECTOR parameterBSS_-COLOR. B11-B14 Spatial Reuse 4 Indicates whether or not spatialreuse is allowed during the transmission of this PPDU Set to the valueof the SPATIAL_REUSE parameter of the TXVECTOR, which contains a valuefrom Table 28-21 (Spatial Reuse field encoding for an HE SU PPDU, HE ERSU PPDU, and HE MU PPDU) (see 27.11.6 (SPATIAL_REUSE)). Set toSRP_DISALLOW to prohibit SRP-based spatial reuse during this PPDU. Setto SRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP- basedspatial reuse and non-SRG OBSS PD-based spatial reuse during this PPDU.For the interpretation of other values see 27.11.6 (SPATIAL_REUSE) and27.9 (Spatial reuse operation).

TABLE 6 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionB15-B17 Bandwidth 3 Set to 0 for 20 MHz. Set to 1 for 40 MHz. Set to 2for 80 MHz non-preamble puncturing mode. Set to 3 for 160 MHz and 80 +80 MHz non-preamble puncturing mode. If the SIGB Compression field is 0:Set to 4 for preamble puncturing in 80 MHz, where in the preamble onlythe secondary 20 MHz is punctured. Set to 5 for preamble puncturing in80 MHz, where in the preamble only one of the two 20 MHz sub- channelsin secondary 40 MHz is punctured. Set to 6 for preamble puncturing in160 MHz or 80 + 80 MHz, where in the primary 80 MHz of the preamble onlythe secondary 20 MHz is punctured. Set to 7 for preamble puncturing in160 MHz or 80 + 80 MHz, where in the primary 80 MHz of the preamble theprimary 40 MHz is present. If the SIGB Compression field is 1 thenvalues 4-7 are reserved. B18-B21 Number Of 4 If the HE-SIG-B Compressionfield is set to 0, indicates HE-SIG-B the number of OFDM symbols in theHE-SIG-B Symbols Or field: MU-MIMO Set to the number of OFDM symbols inthe HE-SIG-B Users field minus 1 if the number of OFDM symbols in theHE-SIG-B field is less than 16; Set to 15 to indicate that the number ofOFDM symbols in the HE-SIG-B field is equal to 16 if Longer Than 16 HESIG-B OFDM Symbols Support sub- field of the HE Capabilities elementtransmitted by at least one recipient STA is 0; Set to 15 to indicatethat the number of OFDM symbols in the HE-SIG-B field is greater than orequal to 16 if the Longer Than 16 HE SIG-B OFDM Symbols Support subfieldof the HE Capabilities element transmitted by all the recipient STAs are1 and if the HE-SIG-B data rate is less than MCS 4 without DCM. Theexact number of OFDM symbols in the HE-SIG-B field is calculated basedon the number of User fields in the HE-SIG-B content channel which isindicated by HE-SIG-B common field in this case. If the HE-SIG-BCompression field is set to 1, indicates the number of MU-MIMO users andis set to the number of NU-MIMO users minus 1 B22 SIGB 1 Set to 0 if theCommon field in HE-SIG-B is present. Compression Set to 1 if the Commonfield in HE-SIG-B is not present.

TABLE 7 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionB21-B22 GI + LTF 2 Indicates the GI duration and HE-LTF size. Size Setto 0 to indicate a 1x HE-LTF and 0.8 μs GI Set to 1 to indicate a 2xHE-LTF and 0.8 μs GI Set to 2 to indicate a 2x HE-LTF and 1.6 μs GI Setto 3 to indicate: a 4x HE-LTF and 0.8 μs GI if both the DCM| and STBCfields are 1. Neither DCM nor STBC shall be applied if both the DCM and.STBC fields are set to 1. a 4x HE-LTF and 3.2 μs GI, otherwise B23-B25NSTS And 3 If the Doppler field is 0, indicates the number of space-Midamble time streams. Periodicity Set to the number of space-timestreams minus 1 For an HE ER SU PPDU, values 2 to 7 are reserved If theDoppler field is 1, then B23-B24 indicates the number of space timestreams, up to 4, and B25 indicates the midamble periodicity B23-B24 isset to the number of space time streams minus 1. For an HE ER SU PPDU,values 2 and 3 are reserved B25 is set to 0 if TXVECTOR parameterMIDAMBLE_PERIODICITY is 10 and set to 1 if TXVECTOR. parameterMIDAMBLE_PERIODICITY is 20. HE-SIG-A2 B0-B6 TXOP 7 Set to 127 toindicate no duration information (HE SU if TXVECTOR parameterTXOP_DURATION PPDU) or is set to UNSPECIFIED. HE-SIG-A3 Set to a valueless than 127 to indicate duration (HE ER SU information for NAV settingand protection of the TXOP as PPDU) follows: If TXVECTOR parameterTXOP_DURATION is less than 512, then B0 is set to 0 and B1-B6 is set tofloor(TXOP_DURATION/8) Otherwise, B0 is set to 1 sad B1-B6 is set tofloor ((TXOP DURATION − 512)/128) where B0 indicates the TXOP lengthgranularity. Set to 0 for 8 μs; otherwise set to 1 for 128 μs. B1-B6indicates the sealed value of the TXOP_DURATION B7 Coding 1 Indicateswhether BCC or LDPC is used: Set to 0 to indicate BCC Set to 1 toindicate LDPC

TABLE 8 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionB8-B10 Number of 3 If the Doppler field is set to 0, indicates theHE-LTF number of HE-LTF symbols: Symbols And Set to 0 for 1 HE-LTFsymbol Midamble Set to 1 for 2 HE-LTF symbols Periodicity Set to 2 for 4HE-LTF symbols Set to 3 for 6 HE-LTF symbols Set to 4 for 8 HE-LTFsymbols Other values are reserved. If the Doppler field is set to 1B8-B9 indicates the number of HE-LTF symbols and B10 indicates midambleperiodicity: B8-B9 is encoded as follows: 0 indicates 1 HE-LTF symbol 1indicates 2 HE-LTF symbols 2 indicates 4 HE-LTF symbols 3 is reservedB10 is set to 0 if the TXVECTOR parameter MIDAMBLE_PERIODICITY is 10 andset to 1 if the TXVECTOR parameter PREAMBLE_PERIODICITY is 20. B11 LDPCExtra 1 Indication of the presence of the extra OFDM symbol Symbolsegment for LDPC. Segment Set to 1 if an extra OFDM symbol segment forLDPC is present. Set to 0 otherwise. B12 STBC 1 In an HE MU PPDU whereeach RU includes no more than 1 user, set to 1 to indicate all RUs areSTBC encoded in the payload, set to 0 to indicate all RUs are not STBCencoded in the payload. STBC does not apply to HE-SIG-B. STBC is notapplied if one or more RUs are used for MU-MIMO allocation. B13-B14Pre-FEC 2 Indicates the pre-FEC padding factor. Padding Set to 0 toindicate a pre-FEC padding factor of 4 Factor Set to 1 to indicate apre-FEC padding factor of 1 Set to 2 to indicate a pre-FEC paddingfactor of 2 Set to 3 to indicate a pre-FEC padding factor of 3 B15 PEDisambiguity 1 Indicates PE disambiguity as defined in 28.3.12 (Packetextension). B16-B19 CRC 4 CRC for bits 0-41 of the HE-SIG-A field (see28.3.10.7.3 (CRC computation)). Bits 0-41 of the HE-SIG-A fieldcorrespond to bits 0-25 of HE-SIG-A1 followed by bits 0-15 ofHE-SIG-A2). B20-B25 Tail 6 Used to terminate the trellis of theconvolutional decoder. Set to 0.

In addition, the HE-SIG-A field of the HE TB PPDU may be defined asfollows.

TABLE 9 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionHE-SIG-A1 B0 Format 1 Differentiate an HE SU PPDU and HE ER SU PPDU froman HE TB PPDU: Set to 0 for an HE TB PPDU B1-B6 BSS Color 6 The BSSColor field is an identifier of the BSS. Set to the value of theTXVECTOR parameter BSS_-COLOR. B7-B10 Spatial Reuse 1 4 Indicateswhether or not spatial reuse is allowed in a subband of the PPDU duringthe transmission of this PPDU, and if allowed, indicates a value that isused to determine a limit on the transmit power of a spatial reusetransmission. If the Bandwidth field indicates 20 MHz, 40 MHz, or 80 MHzthen this Spatial Reuse field applies to the first 20 MHz subband. Ifthe Bandwidth field indicates 160/80 + 80 MHz then this Spatial Reusefield applies to the first 40 MHz subband of the 160 MHz operating band.Set to the value of the SPATIAL_REUSE(1) parameter of the TXVECTOR,which contains a value from Table 28-22 (Spatial Reuse field encodingfor an HE TB PPDU) for an HE TB PPDU (see 27.11.6 (SPATIAL_REUSE)). Setto SRP_DISALLOW to prohibit SRP-based spatial reuse during this PPDU.Set to SRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP- basedspatial reuse and non-SRG OBSS PD-based spatial reuse during this PPDU.For the interpretation of other values see 27.11.6 (SPATIAL_REUSE) and27.9 (Spatial reuse operation).

TABLE 10 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionB11-B14 Spatial Reuse 2 4 Indicates whether or not spatial reuse isallowed in a subband of the PPDU during the transmission of this PPDU,and if allowed, indicates a value that is used to determine a limit onthe transmit power of a spatial reuse transmission. If the Bandwidthfield indicates 20 MHz, 40 MHz, or 80 MHz: This Spatial Reuse fieldapplies to the second 20 MHz subband. If the STA operating channel widthis 20 MHz, then this field is set to the same value as Spatial Reuse 1field. If the STA operating channel width is 40 MHz in the 2.4 GHz band,this field is set to the same value as Spatial Reuse 1 field. If theBandwidth field indicates 160/80 + 80 MHz the this Spatial Reuse fieldapplies to the second 40 MHz subband of the 160 MHz operating band. Setto the value of the SPATIAL_REUSE(2) parameter of the TXVECTOR. whichcontains a value from Table 28-22 (Spatial Reuse field encoding for anHE TB PPDU) for an HE TB PPDU (see 27.11.6 (SPATIAL_REUSE)). Set toSRP_DISALLOW to prohibit SRP-based spatial reuse during this PPDU. Setto SRP_AND_NON_SRG_OBSS_PD_PROIHBITED to prohibit both SRP- basedspatial reuse and non-SRG OBSS PD-based spatial reuse during this PPDU.For the interpretation of other values see 27.11.6 (SPATIAL_REUSE) and27.9 (Spatial reuse operation).

TABLE 11 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionB15-B18 Spatial Reuse 3 4 Indicates whether or not spatial reuse isallowed in a subband of the PPDU during the transmission of this PPDU,and if allowed, indicates a value that is used to determine a limit onthe transmit power of a spatial reuse transmission. If the Bandwidthfield indicates 20 MHz, 40 MHz or 80 MHz: This Spatial Reuse fieldapplies to the third 20 MHz subband. If the STA operating channel widthis 20 MHz or 40 MHz, this field is set to the same value as SpatialReuse 1 field. If the Bandwidth field indicates 160/80 + 80 MHz: ThisSpatial Reuse field applies to the third 40 MHz subband of the 160 MHzoperating band. If the STA operating channel width is 80 + 80 MHz, thisfield is set to the same value as Spatial Reuse 1 field. Set to thevalue of the SPATIAL_REUSE(3) parameter of the TXVECTOR, which containsa value from Table 28-22 (Spatial Reuse field encoding for an HE TBPPDU) for an HE TB PPDU (see 27.11.6 (SPATIAL_REUSE)). Set toSRP_DISALLOW to prohibit SRP-based spatial reuse during this PPDU. Setto SRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP- basedspatial reuse and non-SRG OBSS PD-based spatial reuse during this PPDU.For the interpretation of other values see 27.11.6 (SPATIAL_REUSE) and27.9 (Spatial reuse operation).

TABLE 12 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionB19-B22 Spatial Reuse 4 4 Indicates whether or not spatial reuse isallowed in a subband of the PPDU during the transmission of this PPDU,and if allowed, indicates a value that is used to determine a limit onthe transmit power of a spatial reuse transmission. If the Bandwidthfield indicates 20 MHz, 40 MHz or 80 MHz: This Spatial Reuse fieldapplies to the fourth 20 MHz subband. If the STA operating channel widthis 20 MHz, then this field is set to the same value as Spatial Reuse 1field. If the STA operating channel width is 40 MHz, then this field isset to the same value as Spatial Reuse 2 field. If the Bandwidth fieldindicates 160/80 + 80 MHz: This Spatial Reuse field applies to thefourth 40 MHz subband of the 160 MHz operating band. If the STAoperating channel width is 80 + 80 MHz, then this field is set to samevalue as Spatial Reuse 2 field. Set to the value of the SPATIAL_REUSE(4)parameter of the TXVECTOR, which contains a value from Table 28-22(Spatial Reuse field encoding for an HE TB PPDU) for an HE TB PPDU (see27.11.6 (SPATIAL_REUSE)). Set to SRP_DISALLOW to prohibit SRP-basedspatial reuse during this PPDU. Set toSRP_AND_NON_SRG_OBSS_PD_PROHIBITED to prohibit both SRP- based spatialreuse and non-SRG OBSS PD-based spatial reuse during this PPDU. For theinterpretation of other values see 27.11.6 (SPATIAL_REUSE) and 27.9(Spatial reuse operation). B23 Reserved 1 Reserved and set to 1.NOTE-Unlike other Reserved fields in HE-SIG-A of the HE TB PPDU, B23does not have a corresponding bit in the Trigger frame. B24-B25Bandwidth 2 Set to 0 for 20 MHz Set to 1 for 40 MHz Set to 2 for 80 MHzSet to 3 for 160 MHz and 80 + 80 MHz

TABLE 13 Two Parts of Number HE-SIG-A Bit Field of bits DescriptionHE-SIG-A2 B0-B6 TXOP 7 Set to 127 to indicate no duration information ifTXVECTOR parameter TXOP_DURATION is set to UNSPECIFIED. Set to a valueless than 127 to indicate duration information for NAV setting andprotection of the TXOP as follows: If TXVECTOR parameter TXOP_DURATIONis less than 512, then B0 is set to 0 and B1-B6 is set tofloor(TXOP_DURATION/8) Otherwise, B0 is set to 1 and B1-B6 is set tofloor ((TXOP_DURATION − 512)/128) where B0 indicates the TXOP lengthgranularity. Set to 0 for 8 μs; otherwise set to 1 for 128 μs. B1-B6indicates the scaled value of the TXOP_DURATION B7-B15 Reserved 9Reserved and set to value indicated in the UL HE-SIG-A2 Reservedsubfield in the Trigger frame. B16-B19 CRC 4 CRC of bits 0-41 of theHE-SIG-A field. See 28.3.10.7.3 (CRC computation). Bits 0-41 of theHE-SIG-A field correspond to bits 0-25 of HE-SIG-A1 followed by bits0-15 of HE-SIG-A2). B20-B25 Tail 6 Used to terminate the trellis of theconvolutional decoder. Set to 0.

The HE-SIG-B 1240 may be included only for a multiple-user (MU) PPDU asdescribed above. Basically, the HE-SIG-A 1250 or the HE-SIG-B 1260 mayinclude resource allocation information (or virtual resource allocationinformation) for at least one receiving STA.

FIG. 13 illustrates an example of a PPDU used in the presentspecification.

The PPDU of FIG. 13 may be called in various terms such as an EHT PPDU,a TX PPDU, an RX PPDU, a first type or N-th type PPDU, or the like. Forexample, in the present specification, the PPDU or the EHT PPDU may becalled in various terms such as a TX PPDU, a RX PPDU, a first type orN-th type PPDU, or the like. In addition, the EHT PPDU may be used in anEHT system and/or a new WLAN system enhanced from the EHT system.

The PPDU of FIG. 13 may indicate the entirety or part of a PPDU typeused in the EHT system. For example, the example of FIG. 13 may be usedfor both of a single-user (SU) mode and a multi-user (MU) mode. In otherwords, the PPDU of FIG. 13 may be a PPDU for one receiving STA or aplurality of receiving STAs. When the PPDU of FIG. 13 is used for atrigger-based (TB) mode, the EHT-SIG of FIG. 13 may be omitted. In otherwords, a STA which has received a trigger frame for uplink-MU (UL-MU)may transmit the PPDU in which the EHT-SIG is omitted in the example ofFIG. 13 .

In FIG. 13 , an L-STF to an EHT-LTF may be called a preamble or aphysical preamble, and may begenerated/transmitted/received/obtained/decoded in a physical layer.

A subcarrier spacing of the L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, andEHT-SIG fields of FIG. 13 may be determined as 312.5 kHz, and asubcarrier spacing of the EHT-STF, EHT-LTF, and Data fields may bedetermined as 78.125 kHz. That is, a tone index (or subcarrier index) ofthe L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, and EHT-SIG fields may beexpressed in unit of 312.5 kHz, and a tone index (or subcarrier index)of the EHT-STF, EHT-LTF, and Data fields may be expressed in unit of78.125 kHz.

In the PPDU of FIG. 13 , the L-LTE and the L-STF may be the same asthose in the conventional fields.

The L-SIG field of FIG. 13 may include, for example, bit information of24 bits. For example, the 24-bit information may include a rate field of4 bits, a reserved bit of 1 bit, a length field of 12 bits, a parity bitof 1 bit, and a tail bit of 6 bits. For example, the length field of 12bits may include information related to a length or time duration of aPPDU. For example, the length field of 12 bits may be determined basedon a type of the PPDU. For example, when the PPDU is a non-HT, HT, VHTPPDU or an EHT PPDU, a value of the length field may be determined as amultiple of 3. For example, when the PPDU is an HE PPDU, the value ofthe length field may be determined as “a multiple of 3”+1 or “a multipleof 3”+2. In other words, for the non-HT, HT, VHT PPDI or the EHT PPDU,the value of the length field may be determined as a multiple of 3, andfor the HE PPDU, the value of the length field may be determined as “amultiple of 3”+1 or “a multiple of 3”+2.

For example, the transmitting STA may apply BCC encoding based on a 1/2coding rate to the 24-bit information of the L-SIG field. Thereafter,the transmitting STA may obtain a BCC coding bit of 48 bits. BPSKmodulation may be applied to the 48-bit coding bit, thereby generating48 BPSK symbols. The transmitting STA may map the 48 BPSK symbols topositions except for a pilot subcarrier{subcarrier index −21, −7, +7,+21} and a DC subcarrier{subcarrier index 0}. As a result, the 48 BPSKsymbols may be mapped to subcarrier indices −26 to −22, −20 to −8, −6 to−1, +1 to +6, +8 to +20, and +22 to +26. The transmitting STA mayadditionally map a signal of {−1, −1, −1, 1} to a subcarrier index{−28,−27, +27, +28}. The aforementioned signal may be used for channelestimation on a frequency domain corresponding to 1−28, −27, +27, +281.

The transmitting STA may generate an RL-SIG generated in the same manneras the L-SIG. BPSK modulation may be applied to the RL-SIG. Thereceiving STA may know that the RX PPDU is the HE PPDU or the EHT PPDU,based on the presence of the RL-SIG.

A universal SIG (U-SIG) may be inserted after the RL-SIG of FIG. 13 .The U-SIB may be called in various terms such as a first SIG field, afirst SIG, a first type SIG, a control signal, a control signal field, afirst (type) control signal, or the like.

The U-SIG may include information of N bits, and may include informationfor identifying a type of the EHT PPDU. For example, the U-SIG may beconfigured based on two symbols (e.g., two contiguous OFDM symbols).Each symbol (e.g., OFDM symbol) for the U-SIG may have a duration of 4us. Each symbol of the U-SIG may be used to transmit the 26-bitinformation. For example, each symbol of the U-SIG may betransmitted/received based on 52 data tomes and 4 pilot tones.

Through the U-SIG (or U-SIG field), for example, A-bit information(e.g., 52 un-coded bits) may be transmitted. A first symbol of the U-SIGmay transmit first X-bit information (e.g., 26 un-coded bits) of theA-bit information, and a second symbol of the U-SIB may transmit theremaining Y-bit information (e.g., 26 un-coded bits) of the A-bitinformation. For example, the transmitting STA may obtain 26 un-codedbits included in each U-SIG symbol. The transmitting STA may performconvolutional encoding (i.e., BCC encoding) based on a rate of R=1/2 togenerate 52-coded bits, and may perform interleaving on the 52-codedbits. The transmitting STA may perform BPSK modulation on theinterleaved 52-coded bits to generate 52 BPSK symbols to be allocated toeach U-SIG symbol. One U-SIG symbol may be transmitted based on 65 tones(subcarriers) from a subcarrier index −28 to a subcarrier index +28,except for a DC index 0. The 52 BPSK symbols generated by thetransmitting STA may be transmitted based on the remaining tones(subcarriers) except for pilot tones, i.e., tones −21, −7, +7, +21.

For example, the A-bit information (e.g., 52 un-coded bits) generated bythe U-SIG may include a CRC field (e.g., a field having a length of 4bits) and a tail field (e.g., a field having a length of 6 bits). TheCRC field and the tail field may be transmitted through the secondsymbol of the U-SIG. The CRC field may be generated based on 26 bitsallocated to the first symbol of the U-SIG and the remaining 16 bitsexcept for the CRC/tail fields in the second symbol, and may begenerated based on the conventional CRC calculation algorithm. Inaddition, the tail field may be used to terminate trellis of aconvolutional decoder, and may be set to, for example, “000000”.

The A-bit information (e.g., 52 un-coded bits) transmitted by the U-SIG(or U-SIG field) may be divided into version-independent bits andversion-dependent bits. For example, the version-independent bits mayhave a fixed or variable size. For example, the version-independent bitsmay be allocated only to the first symbol of the U-SIG, or theversion-independent bits may be allocated to both of the first andsecond symbols of the U-SIG. For example, the version-independent bitsand the version-dependent bits may be called in various terms such as afirst control bit, a second control bit, or the like.

For example, the version-independent bits of the U-SIG may include a PHYversion identifier of 3 bits. For example, the PHY version identifier of3 bits may include information related to a PHY version of a TX/RX PPDU.For example, a first value of the PHY version identifier of 3 bits mayindicate that the TX/RX PPDU is an EHT PPDU. In other words, when thetransmitting STA transmits the EHT PPDU, the PHY version identifier of 3bits may be set to a first value. In other words, the receiving STA maydetermine that the RX PPDU is the EHT PPDU, based on the PHY versionidentifier having the first value.

For example, the version-independent bits of the U-SIG may include aUL/DL flag field of 1 bit. A first value of the UL/DL flag field of 1bit relates to UL communication, and a second value of the UL/DL flagfield relates to DL communication.

For example, the version-independent bits of the U-SIG may includeinformation related to a TXOP length and information related to a BSScolor ID.

For example, when the EHT PPDU is divided into various types (e.g.,various types such as an EHT PPDU related to an SU mode, an EHT PPDUrelated to a MU mode, an EHT PPDU related to a TB mode, an EHT PPDUrelated to extended range transmission, or the like), informationrelated to the type of the EHT PPDU may be included in theversion-dependent bits of the U-SIG.

For example, the U-SIG may include: 1) a bandwidth field includinginformation related to a bandwidth; 2) a field including informationrelated to an MCS scheme applied to EHT-SIG; 3) an indication fieldincluding information regarding whether a dual subcarrier modulation(DCM) scheme is applied to EHT-SIG; 4) a field including informationrelated to the number of symbol used for EHT-SIG; 5) a field includinginformation regarding whether the EHT-SIG is generated across a fullband; 6) a field including information related to a type of EHT-LTF/STF;and 7) information related to a field indicating an EHT-LTF length and aCP length.

Preamble puncturing may be applied to the PPDU of FIG. 13 . The preamblepuncturing implies that puncturing is applied to part (e.g., a secondary20 MHz band) of the full band. For example, when an 80 MHz PPDU istransmitted, a STA may apply puncturing to the secondary 20 MHz band outof the 80 MHz band, and may transmit a PPDU only through a primary 20MHz band and a secondary 40 MHz band.

For example, a pattern of the preamble puncturing may be configured inadvance. For example, when a first puncturing pattern is applied,puncturing may be applied only to the secondary 20 MHz band within the80 MHz band. For example, when a second puncturing pattern is applied,puncturing may be applied to only any one of two secondary 20 MHz bandsincluded in the secondary 40 MHz band within the 80 MHz band. Forexample, when a third puncturing pattern is applied, puncturing may beapplied to only the secondary 20 MHz band included in the primary 80 MHzband within the 160 MHz band (or 80+80 MHz band). For example, when afourth puncturing is applied, puncturing may be applied to at least one20 MHz channel not belonging to a primary 40 MHz band in the presence ofthe primary 40 MHz band included in the 80 MHaz band within the 160 MHzband (or 80+80 MHz band).

Information related to the preamble puncturing applied to the PPDU maybe included in U-SIG and/or EHT-SIG. For example, a first field of theU-SIG may include information related to a contiguous bandwidth, andsecond field of the U-SIG may include information related to thepreamble puncturing applied to the PPDU.

For example, the U-SIG and the EHT-SIG may include the informationrelated to the preamble puncturing, based on the following method. Whena bandwidth of the PPDU exceeds 80 MHz, the U-SIG may be configuredindividually in unit of 80 MHz. For example, when the bandwidth of thePPDU is 160 MHz, the PPDU may include a first U-SIG for a first 80 MHzband and a second U-SIG for a second 80 MHz band. In this case, a firstfield of the first U-SIG may include information related to a 160 MHzbandwidth, and a second field of the first U-SIG may include informationrelated to a preamble puncturing (i.e., information related to apreamble puncturing pattern) applied to the first 80 MHz band. Inaddition, a first field of the second U-SIG may include informationrelated to a 160 MHz bandwidth, and a second field of the second U-SIGmay include information related to a preamble puncturing (i.e.,information related to a preamble puncturing pattern) applied to thesecond 80 MHz band. Meanwhile, an EHT-SIG contiguous to the first U-SIGmay include information related to a preamble puncturing applied to thesecond 80 MHz band (i.e., information related to a preamble puncturingpattern), and an EHT-SIG contiguous to the second U-SIG may includeinformation related to a preamble puncturing (i.e., information relatedto a preamble puncturing pattern) applied to the first 80 MHz band.

Additionally or alternatively, the U-SIG and the EHT-SIG may include theinformation related to the preamble puncturing, based on the followingmethod. The U-SIG may include information related to a preamblepuncturing (i.e., information related to a preamble puncturing pattern)for all bands. That is, the EHT-SIG may not include the informationrelated to the preamble puncturing, and only the U-SIG may include theinformation related to the preamble puncturing (i.e., the informationrelated to the preamble puncturing pattern).

The U-SIG may be configured in unit of 20 MHz. For example, when an 80MHz PPDU is configured, the U-SIG may be duplicated. That is, fouridentical U-SIGs may be included in the 80 MHz PPDU. PPDUs exceeding an80 MHz bandwidth may include different U-SIGs.

The EHT-SIG of FIG. 13 may include control information for the receivingSTA. The EHT-SIG may be transmitted through at least one symbol, and onesymbol may have a length of 4 us. Information related to the number ofsymbols used for the EHT-SIG may be included in the U-SIG.

The PPDU of FIG. 13 may be determined (or identified) as an EHT PPDUbased on the following method.

A receiving STA may determine a type of an RX PPDU as the EHT PPDU,based on the following aspect. For example, the RX PPDU may bedetermined as the EHT PPDU: 1) when a first symbol after an L-LTF signalof the RX PPDU is a BPSK symbol; 2) when RL-SIG in which the L-SIG ofthe RX PPDU is repeated is detected; and 3) when a result of applying“modulo 3” to a value of a length field of the L-SIG of the RX PPDU isdetected as “0”. When the RX PPDU is determined as the EHT PPDU, thereceiving STA may detect a type of the EHT PPDU (e.g., anSU/MU/Trigger-based/Extended Range type), based on bit informationincluded in a symbol after the RL-SIG of FIG. 13 . In other words, thereceiving STA may determine the RX PPDU as the EHT PPDU, based on: 1) afirst symbol after an L-LTF signal, which is a BPSK symbol; 2) RL-SIGcontiguous to the L-SIG field and identical to L-SIG; 3) L-SIG includinga length field in which a result of applying “modulo 3” is set to “0”;and 4) a 3-bit PHY version identifier of the aforementioned U-SIG (e.g.,a PHY version identifier having a first value).

For example, the receiving STA may determine the type of the RX PPDU asthe HE PPDU, based on the following aspect. For example, the RX PPDU maybe determined as the HE PPDU: 1) when a first symbol after an L-LTFsignal is a BPSK symbol; 2) when RL-SIG in which the L-SIG is repeatedis detected; and 3) when a result of applying “modulo 3” to a value of alength field of the L-SIG is detected as “1” or “2”.

For example, the receiving STA may determine the type of the RX PPDU asa non-HT, HT, and VHT PPDU, based on the following aspect. For example,the RX PPDU may be determined as the non-HT, HT, and VHT PPDU: 1) when afirst symbol after an L-LTF signal is a BPSK symbol; and 2) when RL-SIGin which L-SIG is repeated is not detected. In addition, even if thereceiving STA detects that the RL-SIG is repeated, when a result ofapplying “modulo 3” to the length value of the L-SIG is detected as “0”,the RX PPDU may be determined as the non-HT, HT, and VHT PPDU.

In the following example, a signal represented as a (TX/RX/UL/DL)signal, a (TX/RX/UL/DL) frame, a (TX/RX/UL/DL) packet, a (TX/RX/UL/DL)data unit, (TX/RX/UL/DL) data, or the like may be a signaltransmitted/received based on the PPDU of FIG. 13 . The PPDU of FIG. 13may be used to transmit/receive frames of various types. For example,the PPDU of FIG. 13 may be used for a control frame. An example of thecontrol frame may include a request to send (RTS), a clear to send(CTS), a power save-poll (PS-poll), BlockACKReq, BlockAck, a null datapacket (NDP) announcement, and a trigger frame. For example, the PPDU ofFIG. 13 may be used for a management frame. An example of the managementframe may include a beacon frame, a (re-)association request frame, a(re-)association response frame, a probe request frame, and a proberesponse frame. For example, the PPDU of FIG. 13 may be used for a dataframe. For example, the PPDU of FIG. 13 may be used to simultaneouslytransmit at least two or more of the control frame, the managementframe, and the data frame.

FIG. 14 illustrates an example of a modified transmission device and/orreceiving device of the present specification.

Each device/STA of the sub-figure (a)/(b) of FIG. 1 may be modified asshown in FIG. 14 . A transceiver 630 of FIG. 14 may be identical to thetransceivers 113 and 123 of FIG. 1 . The transceiver 630 of FIG. 14 mayinclude a receiver and a transmitter.

A processor 610 of FIG. 14 may be identical to the processors 111 and121 of FIG. 1 . Alternatively, the processor 610 of FIG. 14 may beidentical to the processing chips 114 and 124 of FIG. 1 .

A memory 620 of FIG. 14 may be identical to the memories 112 and 122 ofFIG. 1 . Alternatively, the memory 620 of FIG. 14 may be a separateexternal memory different from the memories 112 and 122 of FIG. 1 .

Referring to FIG. 14 , a power management module 611 manages power forthe processor 610 and/or the transceiver 630. A battery 612 suppliespower to the power management module 611. A display 613 outputs a resultprocessed by the processor 610. A keypad 614 receives inputs to be usedby the processor 610. The keypad 614 may be displayed on the display613. A SIM card 615 may be an integrated circuit which is used tosecurely store an international mobile subscriber identity (IMSI) andits related key, which are used to identify and authenticate subscriberson mobile telephony devices such as mobile phones and computers.

Referring to FIG. 14 , a speaker 640 may output a result related to asound processed by the processor 610. A microphone 641 may receive aninput related to a sound to be used by the processor 610.

Hereinafter, technical features of channel bonding supported by the STAof the present disclosure will be described.

For example, in an IEEE 802.11n system, 40 MHz channel bonding may beperformed by combining two 20 MHz channels. In addition, 40/80/160 MHzchannel bonding may be performed in the IEEE 802.11ac system.

For example, the STA may perform channel bonding for a primary 20 MHzchannel (P20 channel) and a secondary 20 MHz channel (S20 channel). Abackoff count/counter may be used in the channel bonding process. Thebackoff count value may be chosen as a random value and decrementedduring the backoff interval. In general, when the backoff count valuebecomes 0, the STA may attempt to access the channel.

During the backoff interval, when the P20 channel is determined to be inthe idle state and the backoff count value for the P20 channel becomes0, the STA, performing channel bonding, determines whether an S20channel has maintained an idle state for a certain period of time (forexample, point coordination function interframe space (PIFS)). If theS20 channel is in an idle state, the STA may perform bonding on the P20channel and the S20 channel. That is, the STA may transmit a signal(PPDU) through a 40 MHz channel (that is, a 40 MHz bonding channel)including a P20 channel and the S20 channel.

FIG. 15 illustrates an example of channel bonding. As shown in FIG. 15 ,the primary 20 MHz channel and the secondary 20 MHz channel may make upa 40 MHz channel (primary 40 MHz channel) through channel bonding. Thatis, the bonded 40 MHz channel may include a primary 20 MHz channel and asecondary 20 MHz channel.

Channel bonding may be performed when a channel contiguous to theprimary channel is in an idle state. That is, the Primary 20 MHzchannel, the Secondary 20 MHz channel, the Secondary 40 MHz channel, andthe Secondary 80 MHz channel can be sequentially bonded. However, if thesecondary 20 MHz channel is determined to be in the busy state, channelbonding may not be performed even if all other secondary channels are inthe idle state. In addition, when it is determined that the secondary 20MHz channel is in the idle state and the secondary 40 MHz channel is inthe busy state, channel bonding may be performed only on the primary 20MHz channel and the secondary 20 MHz channel.

Hereinafter, preamble puncturing supported by a STA in the presentdisclosure will be described.

For example, in the example of FIG. 15 , if the Primary 20 MHz channel,the Secondary 40 MHz channel, and the Secondary 80 MHz channel are allin the idle state, but the Secondary 20 MHz channel is in the busystate, bonding to the secondary 40 MHz channel and the secondary 80 MHzchannel may not be possible. In this case, the STA may configure a 160MHz PPDU and may perform a preamble puncturing on the preambletransmitted through the secondary 20 MHz channel (for example, L-STF,L-LTF, L-SIG, RL-SIG, U-SIG, HE-SIG-A, HE-SIG-B, HE-STF, HE-LTF,EHT-SIG, EHT-STF, EHT-LTF, etc.), so that the STA may transmit a signalthrough a channel in the idle state. In other words, the STA may performpreamble puncturing for some bands of the PPDU. Information on preamblepuncturing (for example, information about 20/40/80 MHz channels/bandsto which puncturing is applied) may be included in a signal field (forexample, HE-SIG-A, U-SIG, EHT-SIG) of the PPDU.

Hereinafter, technical features of a multi-link (ML) supported by a STAof the present disclosure will be described.

The STA (AP and/or non-AP STA) of the present disclosure may supportmulti-link (ML) communication. ML communication may refer tocommunication supporting a plurality of links. The link related to MLcommunication may include channels of the 2.4 GHz band shown in FIG. 9 ,the 5 GHz band shown in FIG. 10 , and the 6 GHz band shown in FIG. 11(for example, 20/40/80/160/240/320 MHz channels).

A plurality of links used for ML communication may be set in variousways. For example, a plurality of links supported by one STA for MLcommunication may be a plurality of channels in a 2.4 GHz band, aplurality of channels in a 5 GHz band, and a plurality of channels in a6 GHz band. Alternatively, a plurality of links supported by one STA forML communication may be a combination of at least one channel in the 2.4GHz band (or 5 GHz/6 GHz band) and at least one channel in the 5 GHzband (or 2.4 GHz/6 GHz band). Meanwhile, at least one of the pluralityof links supported by one STA for ML communication may be a channel towhich preamble puncturing is applied.

The STA may perform an ML setup to perform ML communication. The MLsetup may be performed based on a management frame or control frame suchas a Beacon, a Probe Request/Response, an Association Request/Response,and the like. For example, information about ML setup may be included inan element field included in a Beacon, a Probe Request/Response, anAssociation Request/Response, and the like.

When ML setup is completed, an enabled link for ML communication may bedetermined. The STA may perform frame exchange through at least one of aplurality of links determined as an enabled link. For example, theenabled link may be used for at least one of a management frame, acontrol frame, and a data frame.

When one STA supports multiple links, a transceiver supporting each linkmay operate as one logical STA. For example, one STA supporting twolinks may be expressed as one Multi Link Device (MLD) including a firstSTA for the first link and a second STA for the second link. Forexample, one AP supporting two links may be expressed as one AP MLDincluding a first AP for a first link and a second AP for a second link.In addition, one non-AP supporting two links may be expressed as onenon-AP MLD including a first STA for the first link and a second STA forthe second link.

Hereinafter, more specific features related to the ML setup aredescribed.

The MLD (AP MLD and/or non-AP MLD) may transmit, through ML setup,information on a link that the corresponding MLD can support. Linkinformation may be configured in various ways. For example, informationon the link may include at least one of 1) information on whether theMLD (or STA) supports simultaneous RX/TX operation, 2) information onthe number/upper limit of uplink/downlink links supported by the MLD (orSTA), 3) information on the location/band/resource of theuplink/downlink Link supported by the MLD (or STA), 4) information onthe frame type (management, control, data, etc.) available or preferredin at least one uplink/downlink link, 5) information on ACK policyavailable or preferred in at least one uplink/downlink link, and 6)information on an available or preferred traffic identifier (TID) in atleast one uplink/downlink Link. The TID is related to the priority oftraffic data and is expressed as eight types of values according to theconventional wireless LAN standard. That is, eight TID valuescorresponding to four access categories (ACs) (AC_Background (AC_BK),AC_Best Effort (AC_BE), AC_Video (AC_VI), AC_Voice (AC_VO)) according tothe conventional WLAN standard may be defined.

For example, it may be preset that all TIDs are mapped foruplink/downlink link. Specifically, if negotiation is not made throughML setup, if all TIDs are used for ML communication, and if the mappingbetween uplink/downlink link and TID is negotiated through additional MLsettings, the negotiated TID may be used for ML communication.

Through ML setup, a plurality of links usable by the transmitting MLDand the receiving MLD related to ML communication may be set, and thismay be referred to as an “enabled link”. The “enabled link” may becalled differently in various expressions. For example, it may bereferred to as various expressions such as a first link, a second link,a transmission link, and a reception link.

After the ML setup is completed, the MLD could update the ML setup. Forexample, the MLD may transmit information on a new link when it isnecessary to update information on the link. Information on the new linkmay be transmitted based on at least one of a management frame, acontrol frame, and a data frame.

According to an embodiment, the MLD may include a non-AP MLD and anAP-MLD. The non-AP MLD and the AP-MLD may be classified according to thefunction of an access point (AP). The non-AP MLD and the AP-MLD may bephysically separated or logically separated. For example, when the MLDperforms an AP function, it may be referred to as an AP MLD, and whenthe MLD performs a STA function, it may be referred to as a non-AP MLD.

In the following specification, MLD may refer to a multi-link device.The MLD has one or more connected STAs and has one MAC service accesspoint (SAP) that connects to an upper link layer (Logical Link Control,LLC). MLD may mean a physical device or a logical device. Hereinafter, adevice may mean an MLD.

In addition, the MLD may include at least one STA connected to each linkof the multi-link. For example, the processor of the MLD may control theat least one STA. For example, the at least one STA may be independentlyconfigured and operated. The at least one STA may include a processorand a transceiver, respectively. For example, the at least one STA mayoperate independently regardless of the processor of the MLD.

In the following specification, for the convenience of description, itis described that the MLD (or the processor of the MLD) controls atleast one STA, but is not limited thereto. As described above, the atleast one STA may transmit/receive a signal independently regardless ofthe MLD.

According to an embodiment, the AP MLD or the non-AP MLD may beconfigured in a structure having a plurality of links. In other words,the non-AP MLD may support the plurality of links. The non-AP MLD mayinclude a plurality of STAs. The plurality of STAs may have a link foreach STA.

A multi-link device (MLD) structure in which one AP/non-AP MLD supportsmultiple links is considered as a core technique in the EHT standard(802.11be standard). A STA included in the non-AP MLD may transferinformation on other STAs in the non-AP MLD together through one link.Accordingly, there is an advantage in that an overhead is reduced forframe exchange. In addition, there is an advantage in that link usageefficient of the STA is increased, and power consumption is decreased.

FIG. 16 illustrates an example of the structure of a non-AP MLD.

Referring to FIG. 16 , the non-AP MLD may be configured in a structurehaving a plurality of links. In other words, the non-AP MLD may supportthe plurality of links. The non-AP MLD may include a plurality of STAs.The plurality of STAs may have a link for each STA. Although FIG. 16shows an example of the structure of the non-AP MLD, the structure of anAP MLD may be configured the same as the example of the structure of thenon-AP MLD illustrated in FIG. 16 .

For example, the non-AP MLD may include STA 1, STA 2, and STA 3. STA 1may operate on link 1. Link 1 may be included in a 5 GHz band. STA 2 mayoperate on link 2. Link 2 may be included in a 6 GHz band. STA 3 mayoperate on link 3. Link 3 may be included in the 5 GHz band. The bandsincluding link 1/2/3 are provided for illustration, and link 1/2/3 maybe included in 2.4, 5, and 6 GHz.

An AP/non-AP MLD supporting a multi-link, each AP of the AP MLD and eachSTA of the non-AP MLD may be connected to each link through a link setupprocess. The connected link may be changed to another link or bereconnected by the AP MLD or the non-AP MLD depending on a situation.

In the EHT standard, to reduce power consumption, links may be dividedinto an anchored link or a non-anchored link. The anchored link or thenon-anchored link may be called variously. For example, the anchoredlink may be referred to as a primary link. The non-anchored link may bereferred to as a secondary link.

According to an embodiment, the AP MLD supporting the multi-link maymange each link by designating each link as an anchored link or anon-anchored link. The AP MLD may support one or more links among aplurality of links as anchored links. The non-AP MLD may select and useone or more anchored links thereof from an anchored link list (a list ofanchored links supported by the AP MLD).

For example, the anchored link may be used not only for a frame exchangefor synchronization but also for a non-data frame exchange (i.e., abeacon and management frame exchange). The non-anchored link may be usedonly for a data frame exchange.

The non-AP MLD may watch (or monitor) only the anchored link to receivea beacon and a management frame during an idle period. Therefore, thenon-AP MLD needs to be connected to at least one anchored link toreceive a beacon and a management frame. The one or more anchored linksneed to always maintain an enabled state. However, the non-anchored linkis used only for a data frame exchange. Therefore, a STA correspondingto the non-anchored link (or a STA connected to the non-anchored link)may enter a doze during the idle period in which the channel/link is notused. Accordingly, it is possible to reduce power consumption.

Embodiment for Link Chance and Reconnection

According to an embodiment, each link between the AP MLD and the non-APMLD may be determined in an association or (re)association process. TheAP MLD and the non-AP MLD may perform a frame exchange through theconnected link. A specific embodiment in which the AP MLD and the non-APMLD are connected through a link setup process may be described withreference to FIG. 17 .

FIG. 17 illustrates an example in which the AP MLD and the non-AP MLDare connected through a link setup process.

Referring to FIG. 17 , the AP MLD may include AP 1, AP 2, and AP 3. Thenon-AP MLD may include STA 1 and STA 2. AP 1 and STA 1 may be connectedthrough link 1. AP 2 and STA 2 may be connected through link 2.

For example, AP 1 and STA 1 may be connected through link 1 through afirst link setup process. AP 2 and STA 2 may be connected through link 2through a second link setup process. In another example, the AP MLD andthe non-AP MLD may be connected through a single link setup process. Inother words, the AP MLD and the non-AP MLD may be connected through link1 and link 2 based on the single link setup process.

As described above, each AP and each STA may perform a frame exchangethrough a connected link. In addition, through one link, information onother APs related to a different link or other STAs related to thedifferent link may be transmitted and received.

However, after this link setup process, the AP MLD or the non-AP MLD mayrequest a link change or reconnection for a more efficient frameexchange (e.g., load balancing or interference avoiding) depending on asituation/environment.

An embodiment related to a link change or reconnection may be describedwith reference to FIG. 18 .

FIG. 18 illustrates an example in which a link is changed orreconnected.

Referring to FIG. 18 , STA 2 is conventionally connected to AP 2.Subsequently, excessive data loads may be generated in AP 2. STA 2 maybe reconnected to AP 3 with a relatively small data load. In this case,the AP MLD and the non-AP MLD may perform an efficient data exchange.

FIG. 19 illustrates a specific example in which a link is changed orreconnected.

Referring to FIG. 19 , AP 1 of the AP MLD may be connected to STA 1 ofthe non-AP MLD through link 1. AP 2 of the AP MLD may be connected toSTA 2 of the non-AP MLD through link 2. Subsequently, STA 2 mayattempt/request a connection to AP 3 through a link change orreconnection, and STA 2 may be connected to AP 3 through link 2 based onthe link change or reconnection.

According to an embodiment, the non-AP MLD and the AP MLD may request alink transition to improve performance. The AP MLD and the non-AP MLDmay transmit/receive/exchange various pieces of information on eachcurrent link and information on a link state. Accordingly, the AP MLDand the non-AP MLD may select a link more suitable for transmitting andreceiving a signal based on the various pieces of information on eachcurrent link and the link state, and may transmit the foregoinginformation to help the selection. For example, the various pieces ofinformation on each current link may include information on a datatraffic load for each link and a channel access capability betweenlinks. For example, the link state may be set to “disabled” or“enabled”.

In the following specification, a process in which the AP MLD/non-AP MLDnegotiates with the non-AP MLD/AP MLD to request a change orreconnection to a link other than the connected link to improveperformance may be referred to as a “link switching negotiation”. The“link switching negotiation” may be referred to as various terms, andmay be changed.

In the link switching negotiation process, the non-AP MLD (or AP MLD)may make a request to change a link connected to a specific STA toanother link, and the AP MLD (or non-AP MLD) may respond to this requestusing a request acceptance or rejection message.

For example, as illustrated in FIG. 19 , when a link change is agreed onthrough a link switching negotiation, the STA may perform a linkre-setup process of being reconnected by changing the existing link fromAP 2 to AP 3.

In the following description, link change or reconnection processes maybe divided into those when requested by the AP MLD and when requested bythe non-AP MLD.

Embodiment in which AP MLD Requests Link Change or Reconnection

According to an embodiment, the AP MLD may request a link change orreconnection from the non-AP MLD for efficient data transmission. Forexample, for load balancing, the AP MLD may request a STA to change orreconnect to a more efficient link based on data traffic of each AP.

For example, the AP MLD may calculate/identify/determine a link suitablefor STAs of the non-AP MLD based on data traffic load information oneach AP and/or channel access capability information on each link (e.g.,information on a simultaneous TX/RX (STR) capability). Subsequently, theAP MLD may request a link change or reconnection from a STA (or non-APMLD) based on the data traffic load information on each AP and/or thechannel access capability information on each link.

As described above, when requesting the link change, the AP MLD maytransmit information on a link considered to be most suitable to thenon-AP MLD through a request message. For example, the request messagemay include a beacon or a management frame.

In relation to the foregoing embodiment, an element or field includingthe information on the link considered to be most suitable may be newlyproposed. The newly proposed element or field may be defined as a“recommended link”. The “recommended link” is provided for illustration,and a specific element or field name may be changed.

Recommend link (element/field): An element or field for the AP MLD torecommend a link most suitable for the STA of the non-AP MLD based onvarious pieces of information on each link (e.g., a data load for eachlink). For example, the recommend link (element/field) may be indicatedas link ID information or AP BSS information of the AP MLD. In otherwords, the recommend link (element/field) may include the link IDinformation or the AP BSS information of the AP MLD.

According to an embodiment, the recommend link (element/field) may beoptionally included in a link switching response and transmitted. Forexample, the STA may establish a connection to the link recommended bythe AP based on the element/field (i.e., the recommend link). In anotherexample, the STA may request a connection to a link different from theindicated link based on the element/field (i.e., the recommend Link) andadditional information possessed by the STA.

A specific signal exchange process between the AP MLD and the non-AP MLDaccording to the foregoing embodiment may be described with reference toFIG. 20 .

FIG. 20 illustrates the operations of the AP MLD and the non-AP MLD forthe link change or reconnection.

Referring to FIG. 20 , in a situation in which STA 2 is connected to AP2 through link 2, enormous data traffic may be concentrated in AP 2. Inother words, in the situation in which the STA 2 is connected to the AP2 through link 2, enormous data traffic may be generated in the AP 2.

The AP MLD (or AP 2) may request the non-AP MLD (or STA 2) to reconnectto AP 3 which has relatively few STA connections. A message forrequesting a reconnection is generally transmitted to a STA (i.e., STA2) that wants to reconnect, but may be transmitted to any STA (i.e.,other STAs) depending on a situation (e.g., a channel state or linkstate). In other words, a STA to which the request message forrequesting a reconnection (e.g., a link switching request frame) istransmitted may be changed based on the channel state or the link state.

For example, the STA (i.e., STA 2) having received the request messagefor requesting the reconnection may transmit a response message of“Accept” (e.g., a link switching response frame) when accepting therequest. In another example, when the STA (i.e., STA 2) may transmit aresponse message of “Decline” when rejecting the request.

In general, the STA (i.e., STA 2) accepting the reconnection transmitthe response message via the existing link (the connected link beforethe reconnection), but the response message may also be transmittedthrough any link (i.e., another STA) by using a characteristic of themulti-link.

When STA 2 accepts a link reconnection request, STA 2 may bedisconnected from existing AP 2 and may request a link reconnection toAP 3 after transmitting a response message. Here, a reconnection requestprocess may be performed in the same manner as the existing link setupprocess between the MLDs. After a link setup process between AP 3 andSTA 2 is completed, STA 2 may perform a frame exchange with AP 3 throughlink 2.

However, when STA 2 rejects the link reconnection request, STA 2 and AP2 may use the existing connected link (i.e., link 2) as it is.

According to an embodiment, when the AP recommends a suitable link whenrequesting a link change from the STA, the STA may or may not change thelink to the recommended link. For example, the AP may use the foregoingrecommend link to recommend the link suitable for the STA.

For example, the STA may accept the link change via the response messageto the request message for requesting the reconnection from the AP. TheSTA may accept/identify the link change via the recommended link, andmay request another link change from the AP based on information otherthan information included in the request message.

Accordingly, the AP needs to notify the STA of whether to accept theresponse message. To this end, the AP may transmit a confirmationmessage (e.g., a link switching confirmation frame) to the STA inresponse to the response message (e.g., the link switching responseframe) from the STA.

Specific operations of the AP MLD and the non-AP MLD of the foregoingembodiment may be described with reference to FIG. 21 .

FIG. 21 illustrates the operations of the AP MLD and the non-AP MLD fora link change or reconnection.

Referring to FIG. 21 , AP 2 may request a link change includingrecommended link information from STA 2. In other words, AP 2 maytransmit a link switching request frame including the recommended linkinformation to STA 2.

STA 2 may transmit whether to accept a link request through a linkswitching response frame.

For example, when accepting link switching, STA 2 may transmit the linkswitching response frame link including information on a link to bechanged. Here, the information on the link to be changed may or may notbe the same as a recommended link.

In another example, when STA 2 responds with the link switching responseframe by selecting a link other than the recommended link provided by AP2, the AP may transmit a message with respect to whether to finallyaccept the link to the STA. The message may be referred to as a linkswitching confirmation frame.

For example, AP 2 may accept the link change to the link designated bySTA 2 through the link switching confirmation frame. STA 2 may attemptthe link change to the link designated by STA 2 based on the linkswitching confirmation frame.

In another example, AP 2 may reject the link change to the linkdesignated by STA 2 through the link switching confirmation frame. STA 2and AP 2 may maintain a connection via the existing connected linkwithout changing the link.

The embodiment illustrated in FIG. 21 may be applied even when the APtransmits the link switching request frame without including therecommended link information. For example, when the AP (e.g., AP 2)transmits a link switching request frame to the STA (e.g., STA 2)without recommended link information, the STA may directly designate alink to be changed based on pieces of information possessed by the STA,and may respond to the AP with a link switching response frame. Even inthis case, the AP needs to finally transmit a link switchingconfirmation frame for acceptance. Accordingly, an embodiment in whichthe AP transmits a link switching confirmation frame may be applied evenwhen recommended link information is not included in link switchingrequest frame.

Embodiment in which Non-AP MLD Requests Link Change or Reconnection

According to an embodiment, the non-AP MLD may request a link change orreconnection from the AP MLD for efficient data transmission. Forexample, to use an STR capability in data transmission, the non-AP MLDmay request the AP MLD to change or reconnect a connected link.

FIG. 22 illustrates the operations of the AP MLD and the non-AP MLD fora link change or reconnection.

Referring to FIG. 22 , the AP MLD and the non-AP MLD may perform a linkswitching negotiation. STA 2 of the non-AP MLD may transmit a linkswitching request frame to AP 2 of the AP MLD. AP 2 of the AP MLD maytransmit a link switching response frame to STA 2 of the non-AP MLD inresponse to the link switching request frame. The link switching requestframe or the link switching response frame may be transmitted andreceived through a link to be changed, but is not limited thereto. Thelink switching request frame or the link switching response frame may betransmitted and received through various links in addition to the linkto be changed.

Specifically, when STA 2 of the non-AP MLD determines that a direct linkchange is needed, STA 2 may directly reselect a suitable link, and mayrequest a link change from the AP MLD. For example, in a case where apreviously connected link is in a busy state for a long time and whenSTA 2 wants to obtain QoS for data transmission, STA 2 may determinethat a link change is needed and may request a link change from the APMLD. STA 2 may transmit a link change request message (i.e., a linkswitching request frame) to request the link change.

For example, upon receiving the link change request message, the AP MLDmay transmit a response message of “Accept” when accepting the request.

In another example, upon receiving the link change request message, theAP MLD may transmit a response message of “Decline” when rejecting therequest.

For example, STA 2 may transmit the link change request message (i.e.,the link switching request frame) including information on a STA tochange a link (e.g., a STA ID) and information on a link to be changed(e.g., a link ID or AP BSS information).

When the AP MLD accepts the request, STA 2 receiving the responsemessage of “Accept” may perform a link re-setup process to reconnect toa reselected AP (i.e., AP 3).

However, when the AP MLD rejects the request, STA 2 may continue to usethe previously connected link.

In the following specification, a link re-setup process performed by aSTA to reconnect to a reselected link (i.e., another link) after linkswitching negotiation may be proposed. The link re-setup process may becalled variously, and for convenience of description, a processperformed by a STA to reconnect to a reselected link (i.e., anotherlink) may be referred to as a link re-setup process hereinafter.

Specifically, a link switching method for eliminating overhead in a linkre-setup process that occurs when a STA changes a link may be proposed.According to the link switching method, it is possible to improveoperational performance of a STA and an AP. In addition, a linkswitching method for power saving may also be proposed below. Accordingto the link switching method for power saving, it is possible to reducepower consumption of a STA.

Link Re-Setup Process for Link Switching after Link SwitchingNegotiation

In the following specification, a link switching method (or anembodiment of link switching) applicable for efficient link re-setupafter the foregoing link switching negotiation process may be proposed.In the following specification, the link switching method may bedescribed in the following order.

(0) Various embodiments of link re-setup process

(1) Information transmission method when link switching request istriggered by AP

(2) Information transmission method when link switching request istriggered by STA

(3) Link switching method considering power saving

(4) Definitions of new frame and element for link re-setup of STA and APMLD after link switching

(5) Link re-setup process of non-AP MLD according to link switching case

(5)-1) Link re-setup process when STA performs link switching todifferent AP MLD

(5)-2) Link re-setup process when STA performs link switching todifferent link of connected AP MLD

(5)-3) Link re-setup process for reducing frame overhead when STAperforms link switching to different link of connected AP MLD

(0) Various Embodiments of Link Re-Setup Process

An AP MLD and a non-AP MLD may propose a suitable link for a STA for achange and may agree on a link change with each other through a linkswitching negotiation process. Subsequently, the STA may attempt tochange to a reselected link in this process.

For the STA to exchange data with a changed AP (i.e., a new AP connectedthrough the changed link), the STA needs to perform connection re-setupwith the changed AP. To perform the connection re-setup with the changedAP, the STA needs to perform a (re)association process with the APconnected through the changed link. For example, a legacy (re)association frame used before the EHT standard may be reused as a frameused in the (re)association process. In another example, a new frame maybe defined as a frame used in the (re)association process. A specificexample of this frame may be described in “(4) Definitions of new frameand element for link re-setup of STA and AP MLD after link switching”.

Specific operations of the AP and the STA according to the foregoingembodiment may be described with reference to FIG. 23 .

FIG. 23 illustrates an example of a link re-setup process.

Referring to FIG. 23 , the AP MLD and the non-AP MLD may agree on achanged link through a link switching negotiation process. For example,STA 2 may transmit a link switching request frame to AP 2. AP 2 maytransmit a link switching response frame. According to the linkswitching negotiation process, STA 2 and AP 2 may agree to change a linkconnected to STA 2 (i.e., a link between STA 2 and AP 2) to a linkbetween STA 2 and AP 3.

For convenience of description, the link between STA 2 and AP 2 may bereferred to as an existing link, and the link between STA 2 and AP 3 maybe referred to as a changed link.

After moving to the changed link, STA 2 may request link re-setup (i.e.,(re)association) from a changed AP (i.e., AP 3) in the changed link. Inthis case, STA 2 may perform an association process for exchangingvarious pieces of information with the changed link.

After completing the association with the changed AP, STA 2 may receivea beacon from the changed AP (i.e., AP 3). After obtaining sufficientinformation, STA 2 may perform data exchange with the changed AP.

According to an embodiment, a beacon received from the existingconnected AP (i.e., AP 2) includes the sufficient information on otherAPs (i.e., AP 3), and thus STA 2 may already have the sufficientinformation. In this case, an operation performed by STA 2 to receivethe beacon in the changed link may be omitted.

According to an embodiment, a link re-setup request/response frame (orlink re-setup request/response message) may operate as a managementframe. In this case, the AP MLD and the non-AP MLD may perform channelaccess for each frame (or message). An example of specific operations ofthe AP MLD and the non-AP MLD according to the foregoing embodiment maybe described with reference to FIG. 24 .

FIG. 24 illustrates another example of a link re-setup process.

Referring to FIG. 24 , after link switching, the AP MLD (e.g., AP 3) andthe non-AP MLD (e.g., STA 2) may perform a link re-setup process. In thelink re-setup process, the AP MLD and the non-AP MLD may perform channelaccess for each frame.

According to an embodiment, the AP MLD and the non-AP MLD may transmitan ACK frame for each frame. For example, STA 2 of the non-AP MLD maytransmit a link re-setup request frame to AP 3 of the AP MLD. AP 3 maytransmit an ACK frame in response to the link re-setup request frame. Inaddition, AP 3 may transmit a link re-setup response frame to STA 2. STA2 may transmit an ACK frame in response to the link re-setup responseframe.

According to an embodiment, information sharing may be supported betweenentities of an MLD (the AP of the AP MLD or the STA of the non-AP MLD).In this case, before the STA changes the link to the changed AP, a linkre-setup process may be performed. An example of specific operations ofthe AP MLD and the non-AP MLD according to the foregoing embodiment maybe described with reference to FIG. 25 .

FIG. 25 illustrates another example of a link re-setup process.

Referring to FIG. 25 , after agreeing on a link change, STA 2 and AP 2may exchange information for link re-setup through an existing link(i.e., the link between STA 2 and AP 2). Accordingly, STA 2 may agree onlink re-setup with the changed AP (i.e., AP 3) before an actual linkchange. That is, STA 2 may perform the link change and a link re-setupprocess in the existing link at the same time. Subsequently, STA 2 maychange the connected AP to AP 3.

Even though establishing a connection with AP 3, STA 2 may haveinsufficient information to exchange data with AP 3. Accordingly, STA 2may receive a beacon from AP 3, thereby obtaining sufficient informationto exchange data. Subsequently, STA 2 may exchange data with AP 3.

According to an embodiment, a beacon received from the existingconnected AP (i.e., AP 2) includes the sufficient information on otherAPs (i.e., AP 3), and thus STA 2 may already have the sufficientinformation. In this case, an operation performed by STA 2 to receivethe beacon in the changed link may be omitted.

The foregoing operations of the AP MLD and the non-AP MLD may beperformed differently depending on whether a link re-setuprequest/response frame is defined as a management frame or a controlframe.

An example of a channel access operation for each message according towhether a link re-setup request/response frame is defined as amanagement frame or a control frame may be described below.

FIG. 26 illustrates another example of a link re-setup process.

Referring to FIG. 26 , both a link switching request/response frame anda link re-setup request/response frame may operate as a managementframe. In other words, a management frame may be used as a linkswitching request/response frame and a link re-setup request/responseframe. Accordingly, when all frames/messages are transmitted, channelaccess may be performed.

FIG. 27 illustrates another example of a link re-setup process.

Referring to FIG. 27 , a link re-setup request/response frame mayoperate as a control frame. In other words, a control frame may be usedas a link re-setup request/response frame.

FIG. 28 illustrates another example of a link re-setup process.

Referring to FIG. 28 , a control frame may also be used as a linkswitching request/response frame (or a link switching request/responsemessage) like a link re-setup request/response frame (or a link re-setuprequest/response message). Here, a frame exchange process for linkswitching and a frame exchange process for link re-setup may beperformed separately.

According to an embodiment, the STA may perform message exchanges for alink switching negotiation process and for link re-setup in one process.An example of specific operations of the AP MLD and the non-AP MLDaccording to the foregoing embodiment may be described with reference toFIG. 29 .

FIG. 29 illustrates an example of a link switching negotiation processand a link re-setup process.

Referring to FIG. 29 , both a link switching negotiation process and alink re-setup process may be performed within one TXOP. A frame exchangeprocess for link switching and a frame exchange process for linkre-setup may be performed as one process. In this case, since STA 2 doesnot need to perform separate CCA for the link re-setup, signalingoverhead for the link re-setup may be reduced.

According to an embodiment, essential information necessary for link(re)association may be transmitted to the STA to change the link in thelink switching negotiation process. According to this embodiment, it ispossible to additionally reduce frame overhead occurring for linkre-setup.

Therefore, in the following specification, link switching negotiationprocesses may be divided into a case requested by the AP and a caseinitiated by the STA. A method (or an embodiment) of transmittingessential information required for reconnection (i.e., link re-setup) toa changed link after agreement on link switching in each case may bedescribed below.

For example, essential information that the AP transmits to the STA fora link change may be defined as follows but is not limited thereto. Theessential information to be described below may be added as necessary.In addition, the essential information may include all attributesexchanged in an existing association or (re)association frame to improvecompatibility.

-   -   Identification information on AP to change to: Information on AP        to which STA is to be reconnected (e.g. BSS ID or MAC address)    -   Association ID (AID) information: AID information that STA is to        use in changed link

For example, the non-AP STA may continue to use an existing AID value ormay be allocated new AID information by the AP.

For example, when a new AID is allocated, association ID (AID)information may include a new AID value. In another example, when anexisting AID is used, information indicating that the same existing AIDis used may be indicated in a separate field. In another example, the APMLD may omit AID information, thereby transmitting informationindicating that the same existing AID is used to the non-AP STA. Variousmethods for indicating the information indicating that the same existingAID is used may be additionally defined. For example, when the existingAID is reused, the information indicating that the same existing AID isused may be indicated by omitting an AID field or by using only aminimum number of bits. Accordingly, it is possible to reduce existingframe overhead.

-   -   Operating channel information: Information on channel to be used        in changed link    -   Synchronization information: Synchronization information to be        used for frame transmission and reception after link change        (e.g. TSF and next TBTT)    -   Power save mode information: Information on power save mode        being used in changed link (e.g. TWT information and OPS period)    -   TID mapping information: TID mapping information to be applied        in changed link

For example, when the STA changes a link, all TIDs may be applied as adefault value. In another example, when the STA changes a link, the sameTID mapping information as used in the existing link may be used. Inanother example, when the STA changes a link, new TID mappinginformation may be applied according to the status of each link of theAP MLD.

-   -   Etc. (Various pieces of information may be added in addition to        the above examples.)

(1) Information Transmission Method when Link Switching Request isTriggered by AP

According to an embodiment, a link change may be requested by the APMLD. The AP MLD and the non-AP MLD may operate as shown in FIG. 20 andFIG. 21 .

For example, when the STA accepts the link change requested by the AP,the AP may transmit essential information required for the STA toperform link re-setup of a changed link (e.g., pieces of informationtransmitted by the AP via a (re)association message) to the STA by usinga separate message. Upon receiving the essential information, the STAmay change the link to the changed link based on the essentialinformation without a separate (re)association process.

When the STA changes to a link recommended by the AP as in FIG. 20 , anadditional frame (or message) for transmitting the essential informationto the STA is required. For the additional frame (or message), amanagement frame may be used, or a new frame may be defined. An exampleof specific operations of the AP MLD and the non-AP MLD according to theforegoing embodiment may be described with reference to FIG. 30 .

FIG. 30 illustrates an example in which information for link re-setup istransmitted through a separate frame.

Referring to FIG. 30 , the AP may accept a change to a recommended linkthrough a link switching request frame (or message). The AP may transmitseparate link information for a switching frame (or message) includingessential information (or first information) necessary for the STA toperform link re-setup of the recommended link to the STA. Upon receivingthis information, the STA may change a link based on the essentialinformation without a (re)association process.

According to an embodiment, as shown in FIG. 21 , the STA may not changethe link to the link recommended by the AP. In this case, the AP maytransmit essential information (or first information) necessary for linkre-setup to the STA by using a link switching confirmation message. Anexample of specific operations of the AP MLD and the non-AP MLDaccording to the foregoing embodiment may be described with reference toFIG. 31 .

FIG. 31 illustrates an example in which information for link re-setup istransmitted through a confirmation frame.

Referring to FIG. 31 , the AP MLD (or AP 2) may request a link changeincluding a recommended link from STA 2. In this case, STA 2 may acceptthe link change but may select a different link instead of selecting therecommended link.

STA 2 may transmit a link switching response frame (or message)including link information designated by STA 2 to the AP. In response,the AP MLD (or AP 2) may finally accept a changed link through a linkswitching confirmation frame (or message). AP 2 may transmit the linkswitching confirmation frame including essential information forre-setup of the changed link designated by the STA.

According to an embodiment, the AP may transmit a link switching requestframe by including the information for link re-setup of the recommendedlink in advance. An example of specific operations of the AP MLD and thenon-AP MLD according to the foregoing embodiment may be described withreference to FIG. 32 .

FIG. 32 illustrates an example in which information for link re-setup istransmitted through a link switching request frame.

Referring to FIG. 32 , the AP MLD (or AP 2) may transmit a linkswitching request frame by including essential information for linkre-setup of a recommended link in advance. When STA 2 accepts a linkre-setup request, STA 2 may perform link re-setup based on the essentialinformation transmitted by AP 2 without transmitting a separate messageto the recommended link.

However, when STA 2 rejects this request or selects to change to a linkother than the recommended link, the essential information on therecommended link transmitted by AP 2 in advance may be transmissionoverhead.

(2) Information transmission method when link switching request istriggered by STA

According to an embodiment, a link change may be requested by the non-APMLD. The AP MLD and the non-AP MLD may operate as shown in FIG. 22 .

For example, when the AP accepts the link change requested by the STA,the AP may transmit essential information required for the STA toperform link re-setup of a changed link to the STA through a responsemessage (i.e., a link switching response frame (or message) in responseto a link switching request frame (or message) transmitted by the STA).Upon receiving the essential information for the link change through theresponse message, the STA may change a link to the changed link based onthe essential information without a separate (re)association process. Anexample of specific operations of the AP MLD and the non-AP MLDaccording to the foregoing embodiment may be described with reference toFIG. 33 .

FIG. 33 illustrates an example in which information for link re-setup istransmitted through a link switching response frame.

Referring to FIG. 33 , the non-AP MLD (i.e., STA 2) may transmit a linkswitching request frame including information on a changed link selecteddirectly by the non-AP MLD to the AP MLD (or AP 2). The AP MLD (or AP 2)may transmit a link switching response frame.

For example, when the AP MLD (or AP 2) accepts a link change, the AP MLD(or AP 2) may transmit pieces of essential information for link re-setupof the changed link requested by STA 2. For example, the essentialinformation for link re-setup of the changed link requested by STA 2 maybe included in the link switching response frame. In another example,information on all attributes included in an existing (re)associationframe may be included in the link switching response frame.

Upon receiving the link switching response frame, STA 2 may change alink to the changed link based on the received pieces of informationwithout a separate (re)association process.

In another example, when the AP MLD (or AP 2) rejects the request fromSTA 2, the AP MLD (or AP 2) may transmit a link switching response frameincluding a rejection message without the essential information for linkre-setup.

According to the foregoing embodiment, the STA (i.e., STA 2) may receivethe pieces of essential information for link re-setup without anadditional message, thus reducing overhead.

According to an embodiment, the STA to change the link may transmit thelink switching request frame (or message) including pieces ofinformation requiring reconfiguration after the link change.

For example, among attribute information exchanged through a(re)association frame for link (re)association, a parameter value thatis changed or a parameter value that requires reconfiguration in a linkswitch to another AP of the same AP MLD may be transmitted in advance.When a link switching request including a value desired to bereconfigured is transmitted, the AP may transmit a link switchingresponse frame (or message) including link reconfiguration information.An example of specific operations of the AP MLD and the non-AP MLDaccording to the foregoing embodiment may be described with reference toFIG. 34 .

FIG. 34 illustrates an example in which information for link re-setup istransmitted through a link switching request/response frame.

Referring to FIG. 34 , STA 2 may perform link switching from AP 2 to AP3. STA 2 may transmit a link switching request frame (or message)including information indicating AP 3 and information on a TWT desiredto be configured when a link is switched to AP 3.

Subsequently, AP 2 may transmit a link switching response frame (ormessage). The link switching response frame may include a link switchingrequest confirmation message and a confirmation message in response toTWT configuration requested by STA 2. Upon receiving the confirmationmessage, STA 2 may perform link switching to AP 3, and may then operatewith a configured TWT mechanism without exchanging separate frames forTWT configuration.

According to an embodiment, in addition to the information on the TWT,any information that is reconfigurable when STA 2 performs linkswitching to another AP in the AP MLD may be included in the linkswitching request frame (or message).

According to the foregoing embodiment, link switching agreement andagreement for link reconnection may be performed before link switching.In addition, a parameter requiring a frame exchange for reconfigurationafter link switching may be configured before link switching.

According to an embodiment, even when the non-AP MLD requests the linkchange, the essential information for link re-setup may be transmittedthrough a separate message (e.g. a management frame or a new frame)instead of being included in the link switching response frame as in theabove embodiment. An example of specific operations of the AP MLD andthe non-AP MLD according to the foregoing embodiment may be describedwith reference to FIG. 35 .

FIG. 35 illustrates an example in which information for link re-setup istransmitted through a separate frame.

Referring to FIG. 35 , information for link re-setup may be transmittedthrough a separate frame (i.e., a link re-setup information frame). Forexample, essential information for link re-setup may be transmittedthrough a separate frame. However, in this case, since the AP (i.e., AP2) needs to use the separate message, additional overhead may beincurred.

According to an embodiment, a link switching negotiation process and aninformation transmission process for link re-setup may be performedwithin one TXOP. An example of specific operations of the AP MLD and thenon-AP MLD according to the foregoing embodiment may be described withreference to FIG. 36 .

FIG. 36 illustrates an example of a link switching negotiation processand an information transmission process for link re-setup.

Referring to FIG. 36 , both a link switching negotiation process and aninformation transmission process for link re-setup may be performedwithin one TXOP. In this case, since AP 2 does not need to performseparate CCA for information transmission for link re-setup, signalingoverhead may be reduced.

(3) Link switching method considering power saving

According to the foregoing embodiment, when changing a link, the STA andthe AP may change the link based on pieces of essential information forlink re-setup transmitted by the AP without an additional link(re)association process.

In addition to the forgoing embodiment, the AP may also transmitinformation on various power saving modes of the changed link asessential information for link re-setup. For example, the information onthe various power saving modes of the changed link may includeinformation on a next TBTT, TWT information, or information on an OPSperiod. The STA may operate in a power saving mode based on theinformation on the various power saving modes of the changed link. Aspecific example of the above embodiment may be described below.

1) First, according to an embodiment, the STA receiving next TBTTinformation on the changed link from the AP may enter a doze until anext TBTT after the link change. An example of specific operations ofthe AP MLD and the non-AP MLD according to the foregoing embodiment maybe described with reference to FIG. 37 .

FIG. 37 illustrates an example of a power saving operation of a non-APMLD after a link change.

Referring to FIG. 37 , STA 2 may enter a doze state until a next TBTTafter a link change. In other words, STA 2 may operate in the doze stateafter the link change (or after (re)associated with AP 3). STA 2 maychange the state to an awake state at the next TBTT.

Specifically, STA 2 may receive essential information for link re-setupto AP 3 from AP 2 through a link switching negotiation. Here, AP 2 maytransmit next TBTT information on AP 3 included in power saving-relatedinformation. Upon receiving the information, STA 2 may enter the dozestate until the next TBTT after the link change. Accordingly, powerconsumption may be reduced. STA 2 entering the doze may awake accordingto the TBTT, and may receive a beacon from AP 3.

2) Second, according to an embodiment, the STA receiving power savingmode time information on the changed link from the AP may enter the dozestate according to a period of a power saving mode operating in thelink. Similarly to the next TBTT of the above embodiment, the AP maytransmit information (e.g., TWT information and OPS period information)related to the power saving mode operating in the changed link to theSTA before the link change.

Upon receiving the information, the STA may enter the doze stateaccording to an operation of the power saving mode applied to thechanged link, or may enter the doze state immediately after the linkchange. Subsequently, the STA may change the state to the awake stateaccording to the operation of the power saving mode.

According to an embodiment, when the changed link is operating in a TWTpower saving mode, the STA may enter the doze state after the linkchange, and may change the state to the awake state according to the TWTinformation. An example of specific operations of the AP MLD and thenon-AP MLD according to the foregoing embodiment may be described withreference to FIG. 38 .

FIG. 38 illustrates an example of a power saving operation of a non-APMLD after a link change.

Referring to FIG. 38 , STA 2 may operate in the doze state until a nextTWT after a link change. Specifically, STA 2 may obtain TWT information(info) (e.g., a next TWT) from AP 2 before the link change. STA 2 maychange the link to AP 3 and may then operate in the doze state until thenext TWT based on the TWT information, thereby reducing powerconsumption.

In another example, when a link change time is within a TWT period, STA2 may maintain the awake state, and may then operate in the doze stateuntil the next TWT after the TWT period.

According to an embodiment, when the changed link is operating in an OPSpower saving mode, the STA may enter the doze state according to an OPSperiod after the link change. An example of specific operations of theAP MLD and the non-AP MLD according to the foregoing embodiment may bedescribed with reference to FIG. 39 .

FIG. 39 illustrates an example of a power saving operation of a non-APMLD after a link change.

Referring to FIG. 39 , STA 2 may enter a doze state during an OPS periodafter a link change. Specifically, STA 2 may obtain OPS information(info) from the AP MLD (or AP 2) before the link change. For example,the OPS information may include OPS period information.

Subsequently, STA 2 may enter the doze state during an OPS period afterchanging the link to AP 3. Accordingly, power consumption may bereduced.

In another example, when a link change time (or immediately after thelink change) is not the OPS period, STA 2 may maintain the awake state,and may then enter the doze state according to the OPS period.

(4) Definitions of New Frame and Element for Link Re-Setup of STA and APMLD after Link Switching

In the present specification, a need for link re-setup (reconnection)with a changed AP after changing a connected link of the non-AP MLD isdescribed.

For data connection through the changed link, the STA needs to not onlychange a link thereof but also re-set up a link with the changed AP. Fora link change and link re-setup, a (re)association frame defined in theexisting 802.11 standard may be reused. However, since initialmulti-link setup has already been performed between the AP MLD and thenon-AP MLD, using the existing (re)association frame may incurconsiderable overhead.

Therefore, in the following specification, a new frame optimized for theEHT standard may be defined in order to reduce frame overhead describedabove.

An MLD defined in the EHT standard may obtain information on other STAsor APs through another link through a multi-link. Further, theinformation on the other STAs or APs may be shared internally in the MLDthrough sharing between STAs or APs.

Considering the above characteristic of the MLD, when the STA re-sets upthe link with the changed AP after link switching, the STA and thechanged AP do not need to exchange MLD common information (informationthat the MLD commonly has) shared in the initial multi-link setup againafter the link change.

During the initial multi-link setup process, the AP MLD and the non-APMLD need to exchange all information with each other to set up a link.However, in link switching, since a specific STA of the non-AP MLDperforms link reconnection with a specific AP of the AP MLD, allinformation previously exchanged does not necessarily need to beexchanged.

Therefore, when the STA re-sets up a link after link switching,information that has been exchanged in initial multi-link setup and isnot frequently changed and thus does not need to be shared again afterthe initial multi-link setup does not need to be exchanged. In thefollowing specification, a link re-setup frame in which the informationthat does not need to be exchanged is omitted may be proposed.

An example of essential information included in a link re-setup framemay be described below. The link re-setup frame may include a linkre-setup request/response frame. Hereinafter, an example of informationthat may be included in each link re-setup request/response frame isdescribed.

1) Definition of new link re-setup request frame

1)-A. A new link re-setup request frame may include all fields exceptfor information that STAs of the non-AP MLD commonly have among fieldsincluded in a conventional (re)association request frame. For example,the new link re-setup request frame may include all unique informationthat a specific STA of the non-AP MLD has.

1)-B. A new link re-setup request frame may include the information thatthe STAs of the non-AP MLD commonly have among the fields included inthe conventional (re)association request frame. For example, among theinformation that the STAs of the non-AP MLD commonly have, pieces ofinformation that may be changed after initial multi-link setup may beincluded in the new link re-setup request frame.

2) Definition of new link re-setup response frame

2)-A. A new link re-setup response frame may include all fields exceptfor information that STAs of the non-AP MLD commonly have among fieldsincluded in a conventional (re)association request frame. For example,the new link re-setup response frame may include all unique informationthat a specific STA of the non-AP MLD has.

2)-B. A new link re-setup response frame may include the informationthat the STAs of the non-AP MLD commonly have among the fields includedin the conventional (re)association request frame. For example, amongthe information that the STAs of the non-AP MLD commonly have, pieces ofinformation that may be changed after initial multi-link setup may beincluded in the new link re-setup response frame.

When the above link re-setup frames are used, the non-AP MLD and the APMLD may re-set up a link through a lightened frame. In this case, it ispossible to reduce frame overhead incurred in a link change process.

(5) Link Re-Setup Process of Non-AP MLD According to Link Switching Case

According to an embodiment, the STA of the non-AP MLD may switch anoperating link thereof to a different link depending on the situation.This case may be divided into two main types.

First, the STA may switch the operating link thereof to a different APMLD. Second, the STA may switch the operating link thereof to adifferent AP of the AP MLD that is already connected.

For example, when an AP or AP MLD to switch to is an AP with which theSTA has never been previously associated, the STA needs to perform alink re-setup process with respect to the AP or AP MLD.

A different link re-setup process may be applied depending on a linkswitching method of the STA. Therefore, link re-setup processes for twocases may be described below.

(5)-1) Link re-setup process when STA performs link switching todifferent AP MLD

According to an embodiment, the STAs of the non-AP MLD may switch anoperating link thereof to a different AP MLD. In this case, the non-APMLD needs to perform a link re-setup process with the switched AP MLD.An example of specific operations of the AP MLD and the non-AP MLDaccording to the foregoing embodiment may be described with reference toFIG. 40 .

FIG. 40 illustrates an example of a link re-setup operation of a STAwhen the STA switches a link from AP MLD 2 to AP MLD 1.

Referring to FIG. 40 , a non-AP MLD and AP MLD 2 may be connectedthrough link 1 and link 2. For example, STA 1 of the non-AP MLD may beconnected to AP 1 of AP MLD 2 through link 1. STA 2 of the non-AP MLDmay be connected to AP 2 of AP MLD 2 through link 2. Subsequently, thenon-AP MLD may change a link from AP MLD 2 to AP MLD 1.

For example, the non-AP MLD may change both link 1 and link 2 to a linkconnected to AP MLD 1. In another example, STA 2 of the non-AP MLD maychange link 2 to a link connected to AP 2 of AP MLD 1.

According to an embodiment, after switching the link to a different APMLD, the STA of the non-AP MLD may obtain necessary information (e.g., aBSSID and channel information) for starting link re-setup through abeacon or a probe response from the switched link. The STA of the non-APMLD may perform link re-setup based on the necessary information forstarting link re-setup. An example of specific operations of the AP MLDand the non-AP MLD according to the foregoing embodiment may bedescribed with reference to FIG. 41 .

FIG. 41 illustrates an example of a link re-setup process when a link isswitched to a different AP MLD other than a connected AP MLD.

Referring to FIG. 41 , STA 2 of non-AP MLD 1 may switch an operatinglink thereof from AP MLD 2 to AP MLD 3. After switching the link to APMLD 3, STA 2 may obtain pieces of basic information for starting linkre-setup through a beacon. After obtain the information through thebeacon, STA 2 may perform a link re-setup process with respect to AP MLD3.

According to an embodiment, the TBTT information transmission method inconsideration of power saving mentioned in section (3) may also beapplied to the link re-setup process. An example of specific operationsof the AP MLD and the non-AP MLD according to the foregoing embodimentmay be described with reference to FIG. 42 .

FIG. 42 illustrates another example of a link re-setup process when alink is switched to a different AP MLD other than a connected AP MLD.

Referring to FIG. 42 , non-AP MLD 1 (or STA 2) may obtain next TBTTinformation on each AP of AP MLD 3 before link switching. STA 2 ofnon-AP MLD 1 may enter the doze state immediately after the linkswitching. Subsequently, STA 2 may change the state to the awake stateaccording to a TBTT based on the obtained next TBTT information. STA 2,which has changed the state to the awake state, may receive a beacon.

According to the above embodiment, STA 2 may operate in the doze statefor a period until the beacon is received after the link switching.Accordingly, power consumption of STA 2 may be reduced.

(5)-2) Link Re-Setup Process when STA Performs Link Switching toDifferent Link of Connected AP MLD

According to an embodiment, the STAs of the non-AP MLD may switch anoperating link thereof to a different link of a connected AP MLD(associated AP MLD). An example of specific operations of the AP MLD andthe non-AP MLD according to the foregoing embodiment may be describedwith reference to FIG. 43 .

FIG. 43 illustrates another example of a link re-setup process when alink is switched to a different link of a connected AP MLD.

Referring to FIG. 43 , a non-AP MLD and an AP MLD may be connectedthrough link 1 and link 2. For example, STA 1 of the non-AP MLD may beconnected to AP 1 of the AP MLD through link 1. STA 2 of the non-AP MLDmay be connected to AP 2 of the AP MLD through link 2.

STA 2 may re-set up a link to an AP (i.e., AP3) capable of improvingperformance in consideration of cross-link condition information (e.g.,BSS load information) on the AP MLD.

According to an embodiment, the STA may obtain various pieces ofinformation on the AP to switch to (i.e., information necessary toinitiate link re-setup) from a beacon received through the current linkby using an information sharing capability, which is a characteristic ofthe MLD, before link switching. In this case, the STA of the non-AP MLDmay perform a link re-setup process without obtaining informationthrough a beacon or a probe response after link switching to a differentAP of the connected AP MLD.

According to the above embodiment, since the STA does not need to waitto receive a beacon or a probe response after the link switching,network performance may be increased compared to the link re-setupprocess described in section (5)-1). That is, frame overhead may bereduced, and power consumption may be reduced. An example of specificoperations of the AP MLD and the non-AP MLD according to the foregoingembodiment may be described with reference to FIG. 44 .

FIG. 44 illustrates another example of a link re-setup process when alink is switched to a different link of a connected AP MLD.

Referring to FIG. 44 , STA 2 may already obtain information on AP 3 froma beacon of AP 2. STA 2 may perform a link re-setup process withoutwaiting to listen to a beacon after link switching to AP 3.

(5)-3) Link Re-Setup Process for Reducing Frame Overhead when STAPerforms Link Switching to Different Link of Connected AP MLD

The process proposed to reduce frame overhead for link re-setupdescribed in section (2) (e.g., FIG. 33 ) may be applied to the linkre-setup process described in the foregoing embodiment.

FIG. 45 is a flowchart illustrating the operation of a multi-linkdevice.

Referring to FIG. 45 , in operation S4510, the multi-link device maytransmit a request frame for changing a first link to a second link.According to an embodiment, the multi-link device may transmit therequest frame for changing the first link among a plurality of links tothe second link not included in the plurality of links through the firstlink.

For example, the multi-link device may be connected to an AP multi-linkdevice through the plurality of links including the first link. Themulti-link device may include a plurality of STAs relating to theplurality of links. For example, a first STA among the plurality of STAsmay be connected to the first link. In other words, the first STA mayoperate in the first link. Further, the first STA may be connected to afirst AP of the AP multi-link device through the first link.

Accordingly, the multi-link device may transmit a request frame forchanging connection of the first STA from the first link to the secondlink. A second AP of the AP multi-link device may operate in the secondlink. That is, the multi-link device may transmit the request frame forchanging an AP connected to the first STA from the first AP to thesecond AP.

For example, the plurality of links and the second link may be includedin 2.4 GHz, 5 GHz, and 6 GHz bands.

In operation S4520, the multi-link device may receive a response framebased on the request frame. According to an embodiment, the multi-linkdevice may receive the response frame through the first link based onthe request frame.

According to an embodiment, the response frame may include firstinformation on the second link. For example, the first information mayinclude information essentially used to change the first link to thesecond link. For example, the first information may include at least oneof AID information on the second link, operating channel information onthe second link, synchronization information on the second link, ortraffic identifier (TID) mapping information on the second link.

In operation S4530, the multi-link device may change the first link tothe second link based on the response frame. In other words, themulti-link device may change the AP connected to the first STA from thefirst AP to the second AP based on the response frame.

According to an embodiment, the multi-link device may receive a firstbeacon frame before transmitting the request frame. For example, thefirst beacon frame may be transmitted through the first link. Forexample, the first beacon frame may include second information on thesecond link. The second information may be distinguished from the firstinformation.

That is, the multi-link device may first receive the second informationthrough the first beacon frame, and may receive the first informationthat is remaining information required for a link change through theresponse frame. The multi-link device may change the first link to thesecond link based on the first information included in the responseframe and the second information included in the first beacon frame.

According to an embodiment, the first information may includeinformation on a target wake time (TWT) schedule set in the second link.After receiving the first information (or the response frame), themulti-link device may change a link connected to the first STA from thefirst link to the second link.

After the connection of the first STA is changed from the first link tothe second link based on the first information, the multi-link devicemay change the first STA to a power saving mode. For example, after theconnection of the first STA is changed from the first link to the secondlink based on the first information, the multi-link device may changethe first STA to a TWT-based power saving mode. For example, after thefirst link is changed to the second link, the multi-link device maychange the state of the first STA connected to the second link to a dozestate.

For example, the information on the target wake time (TWT) schedule setin the second link may include information on a next TWT. Thus, themulti-link device may change the state of the first STA connected to thesecond link from the doze state to an awake state in the next TWT.

According to an embodiment, the first information may include allinformation necessary for link re-setup. Thus, the multi-link device mayperform the link change without a link re-setup process. In other words,the multi-link device may perform the link change without exchanging anassociation frame. That is, when the link is changed, exchange of theassociation frame may be omitted.

According to an embodiment, the multi-link device may receive a secondbeacon frame through the second link. The second beacon frame mayinclude information for transmitting and receiving data through thesecond link.

For example, the multi-link device may receive the second beacon framethrough the first STA connected to the second link. The multi-linkdevice may transmit uplink (UL) data or may receive downlink (DL) databased on the second beacon frame.

FIG. 46 is a flowchart illustrating the operation of an AP multi-linkdevice.

Referring to FIG. 46 , in operation S4610, the AP multi-link device mayreceive a request frame for changing a first link to a second link froma multi-link device connected through a plurality of links. According toan embodiment, the AP multi-link device may receive the request framefor changing the first link among the plurality of links to the secondlink not included in the plurality of links through the first link fromthe multi-link device connected through the plurality of links.

For example, the AP multi-link device may be connected to the multi-linkdevice through the plurality of links including the first link. The APmulti-link device may include a plurality of APs relating to theplurality of links. The AP multi-link device may include a second AP.The second AP may operate in the second link not included in theplurality of links.

For example, a first AP among the plurality of APs may be connected tothe first link. In other words, the first AP may operate in the firstlink. Further, the first AP may be connected to a first STA of themulti-link device through the first link.

Accordingly, the AP multi-link device may receive a request frame forchanging connection of the first STA of the multi-link device from thefirst link to the second link. That is, the AP multi-link device mayreceive the request frame for changing an AP connected to the first STAfrom the first AP to the second AP.

For example, the plurality of links and the second link may be includedin 2.4 GHz, 5 GHz, and 6 GHz bands.

In operation S4620, the AP multi-link device may transmit a responseframe based on the request frame. According to an embodiment, the APmulti-link device may transmit the response frame through the first linkbased on the request frame.

According to an embodiment, the response frame may include firstinformation on the second link. For example, the first information mayinclude information essentially used to change the first link to thesecond link. For example, the first information may include at least oneof AID information on the second link, operating channel information onthe second link, synchronization information on the second link, ortraffic identifier (TID) mapping information on the second link.

In operation S4630, the AP multi-link device may change the first linkto the second link based on the response frame. In other words, the APmulti-link device may change the AP connected to the first STA from thefirst AP to the second AP based on the response frame.

According to an embodiment, the AP multi-link device may transmit afirst beacon frame before receiving the request frame. For example, thefirst beacon frame may be transmitted through the first link. Forexample, the first beacon frame may include second information on thesecond link. The second information may be distinguished from the firstinformation.

That is, the AP multi-link device may first transmit the secondinformation through the first beacon frame, and may transmit the firstinformation that is remaining information required for a link changethrough the response frame.

According to an embodiment, the first information may includeinformation on a target wake time (TWT) schedule set in the second link.After transmitting the first information (or the response frame), the APmulti-link device may change a link connected to the first STA from thefirst link to the second link. For example, the information on thetarget wake time (TWT) schedule set in the second link may includeinformation on a next TWT.

According to an embodiment, the first information may include allinformation necessary for link re-setup. Thus, the AP multi-link devicemay perform the link change without a link re-setup process. In otherwords, the AP multi-link device may perform the link change withoutexchanging an association frame. That is, when the link is changed,exchange of the association frame may be omitted.

According to an embodiment, the AP multi-link device may transmit asecond beacon frame through the second link. The second beacon frame mayinclude information for transmitting and receiving data through thesecond link.

For example, the AP multi-link device may transmit the second beaconframe through the second AP connected to the second link. The APmulti-link device may receive uplink (UL) data or may transmit downlink(DL) data based on the second beacon frame.

The foregoing technical features of the present specification may beapplied to various devices and methods. For example, the foregoingtechnical features of the present specification may beperformed/supported through the apparatus of FIG. 1 and/or FIG. 14 . Forexample, the foregoing technical features of the present specificationmay be applied to only part of FIG. 1 and/or FIG. 14 . For example, theforegoing technical features of the present specification may beimplemented based on the processing chips 114 and 124 of FIG. 1 , may beimplemented based on the processors 111 and 121 and the memories 112 and122 of FIG. 1 , or may be implemented based on the processor 610 and thememory 620 of FIG. 14 . For example, an apparatus of the presentspecification may include a processor and a memory connected to theprocessor, wherein the processor may be configured to: transmit arequest frame for changing a first link included in a plurality of linksto a second link not included in the plurality of links through thefirst link; receive a response frame through the first link, based onthe request frame, the response frame including first information on thesecond link; and change the first link to the second link based on theresponse frame.

The technical features of the present specification may be implementedbased on a computer-readable medium (CRM). For example, the CRM proposedaccording to the present specification may be encoded with at least onecomputer program including instructions. When executed by at least oneprocessor, the instructions may cause the at least one processor toperform operations including: transmitting a request frame for changinga first link among a plurality of links to a second link not included inthe plurality of links through the first link; receiving a responseframe through the first link, based on the request frame, the responseframe including first information on the second link; and changing thefirst link to the second link based on the response frame. Theinstructions stored in the CRM of the present specification may beexecuted by at least one processor. The least one processor related tothe CRM of the present specification may be the processors 111 and 121or the processing chips 114 and 124 of FIG. 1 or may be the processor610 of FIG. 14 . The CRM of the present specification may be thememories 112 and 122 of FIG. 1 , may be the memory 620 of FIG. 14 , ormay be a separate external memory/storage medium/disk.

The foregoing technical features of this specification are applicable tovarious applications or business models. For example, the foregoingtechnical features may be applied for wireless communication of a devicesupporting artificial intelligence (AI).

Artificial intelligence refers to a field of study on artificialintelligence or methodologies for creating artificial intelligence, andmachine learning refers to a field of study on methodologies fordefining and solving various issues in the area of artificialintelligence. Machine learning is also defined as an algorithm forimproving the performance of an operation through steady experiences ofthe operation.

An artificial neural network (ANN) is a model used in machine learningand may refer to an overall problem-solving model that includesartificial neurons (nodes) forming a network by combining synapses. Theartificial neural network may be defined by a pattern of connectionbetween neurons of different layers, a learning process of updating amodel parameter, and an activation function generating an output value.

The artificial neural network may include an input layer, an outputlayer, and optionally one or more hidden layers. Each layer includes oneor more neurons, and the artificial neural network may include synapsesthat connect neurons. In the artificial neural network, each neuron mayoutput a function value of an activation function of input signals inputthrough a synapse, weights, and deviations.

A model parameter refers to a parameter determined through learning andincludes a weight of synapse connection and a deviation of a neuron. Ahyper-parameter refers to a parameter to be set before learning in amachine learning algorithm and includes a learning rate, the number ofiterations, a mini-batch size, and an initialization function.

Learning an artificial neural network may be intended to determine amodel parameter for minimizing a loss function. The loss function may beused as an index for determining an optimal model parameter in a processof learning the artificial neural network.

Machine learning may be classified into supervised learning,unsupervised learning, and reinforcement learning.

Supervised learning refers to a method of training an artificial neuralnetwork with a label given for training data, wherein the label mayindicate a correct answer (or result value) that the artificial neuralnetwork needs to infer when the training data is input to the artificialneural network. Unsupervised learning may refer to a method of trainingan artificial neural network without a label given for training data.Reinforcement learning may refer to a training method for training anagent defined in an environment to choose an action or a sequence ofactions to maximize a cumulative reward in each state.

Machine learning implemented with a deep neural network (DNN) includinga plurality of hidden layers among artificial neural networks isreferred to as deep learning, and deep learning is part of machinelearning. Hereinafter, machine learning is construed as including deeplearning.

The foregoing technical features may be applied to wirelesscommunication of a robot.

Robots may refer to machinery that automatically process or operate agiven task with own ability thereof. In particular, a robot having afunction of recognizing an environment and autonomously making ajudgment to perform an operation may be referred to as an intelligentrobot.

Robots may be classified into industrial, medical, household, militaryrobots and the like according uses or fields. A robot may include anactuator or a driver including a motor to perform various physicaloperations, such as moving a robot joint. In addition, a movable robotmay include a wheel, a brake, a propeller, and the like in a driver torun on the ground or fly in the air through the driver.

The foregoing technical features may be applied to a device supportingextended reality.

Extended reality collectively refers to virtual reality (VR), augmentedreality (AR), and mixed reality (MR). VR technology is a computergraphic technology of providing a real-world object and background onlyin a CG image, AR technology is a computer graphic technology ofproviding a virtual CG image on a real object image, and MR technologyis a computer graphic technology of providing virtual objects mixed andcombined with the real world.

MR technology is similar to AR technology in that a real object and avirtual object are displayed together. However, a virtual object is usedas a supplement to a real object in AR technology, whereas a virtualobject and a real object are used as equal statuses in MR technology.

XR technology may be applied to a head-mount display (HMD), a head-updisplay (HUD), a mobile phone, a tablet PC, a laptop computer, a desktopcomputer, a TV, digital signage, and the like. A device to which XRtechnology is applied may be referred to as an XR device.

The claims recited in the present specification may be combined in avariety of ways. For example, the technical features of the methodclaims of the present specification may be combined to be implemented asa device, and the technical features of the device claims of the presentspecification may be combined to be implemented by a method. Inaddition, the technical characteristics of the method claim of thepresent specification and the technical characteristics of the deviceclaim may be combined to be implemented as a device, and the technicalcharacteristics of the method claim of the present specification and thetechnical characteristics of the device claim may be combined to beimplemented by a method.

1. A method performed by a multi-link device operating in a plurality oflinks in a wireless local area network system, the method comprising:transmitting a request frame for changing a first link among theplurality of links to a second link not comprised in the plurality oflinks through the first link; receiving a response frame through thefirst link, based on the request frame, the response frame comprisingfirst information on the second link; and changing the first link to thesecond link based on the response frame.
 2. The method of claim 1,further comprising: receiving a first beacon frame before transmittingthe request frame, wherein the first beacon frame comprises secondinformation on the second link, and the second information isdistinguished from the first information.
 3. The method of claim 2,wherein the changing of the first link to the second link based on theresponse frame comprises changing the first link to the second linkbased on the first information comprised in the response frame and thesecond information comprised in the first beacon frame.
 4. The method ofclaim 1, wherein the first information comprises information essentiallyused to change the first link to the second link.
 5. The method of claim1, wherein the first information comprises at least one of associationidentifier (AID) information on the second link, operating channelinformation on the second link, synchronization information on thesecond link, or traffic identifier (TID) mapping information on thesecond link.
 6. The method of claim 1, wherein the first informationcomprises information on a target wake time (TWT) schedule set in thesecond link.
 7. The method of claim 6, further comprising: changing astate of a first station (STA) connected to the second link to a dozestate after the first link is changed to the second link.
 8. The methodof claim 7, further comprising: changing the state of the first STAconnected to the second link from the doze state to an awake state in anext TWT based on the information on the target wake time (TWT) scheduleset in the second link.
 9. The method of claim 1, further comprising:receiving a second beacon frame through the second link, wherein thesecond beacon frame comprises information for transmitting and receivingdata through the second link.
 10. The method of claim 1, wherein thefirst link is comprised in 2.4 GHz, 5 GHz, and 6 GHz bands, and thesecond link is comprised in 2.4 GHz, 5 GHz, and 6 GHz bands.
 11. Amethod performed by an access point (AP) multi-link device operating ina plurality of links and a second link in a wireless local area networksystem, the method comprising: receiving a request frame for changing afirst link among the plurality of links to the second link not comprisedin the plurality of links from a multi-link device connected through theplurality of links; transmitting a response frame to the multi-linkdevice, based on the request frame, the response frame comprising firstinformation on the second link; and changing the first link to thesecond link based on the response frame.
 12. A multi-link device (MLD)operating in a plurality of links in a wireless local area networksystem, the MLD comprising: a first station (STA) connected to a firstlink among the plurality of links; and a processor connected to thefirst STA, wherein the processor is configured to: transmit a requestframe for changing the first link to a second link not comprised in theplurality of links through the first link, receive a response framethrough the first link, based on the request frame, the response framecomprising first information on the second link; and change the firstlink to the second link based on the response frame.
 13. The MLD ofclaim 12, wherein the processor is further configured to receive a firstbeacon frame before transmitting the request frame, the first beaconframe comprises second information on the second link, and the secondinformation is distinguished from the first information.
 14. The MLD ofclaim 12, wherein the first information comprises informationessentially used to change the first link to the second link.
 15. TheMLD of claim 12, wherein the first information comprises information ona target wake time (TWT) schedule set in the second link.
 16. The MLD ofclaim 15, wherein the processor is further configured to change a stateof the first STA to a doze state after the first link is changed to thesecond link.
 17. The MLD of claim 16, wherein the processor is furtherconfigured to change the state of the first STA from the doze state toan awake state in a next TWT based on the information on the target waketime (TWT) schedule set in the second link. 18-20. (canceled)